diff --git a/dom/animation/KeyframeEffectReadOnly.cpp b/dom/animation/KeyframeEffectReadOnly.cpp
index 3882735b30..d588c7b1da 100644
--- a/dom/animation/KeyframeEffectReadOnly.cpp
+++ b/dom/animation/KeyframeEffectReadOnly.cpp
@@ -1268,7 +1268,7 @@ CreateStyleContextForAnimationValue(nsCSSPropertyID aProperty,
   rules.AppendObject(styleRule);
 
   nsStyleSet* styleSet =
-    aBaseStyleContext->PresContext()->StyleSet()->AsGecko();
+    aBaseStyleContext->PresContext()->StyleSet();
 
   RefPtr<nsStyleContext> styleContext =
     styleSet->ResolveStyleByAddingRules(aBaseStyleContext, rules);
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index 52117bf7f6..a5b67b6b13 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -245,8 +245,6 @@
 #include "mozilla/dom/BoxObject.h"
 #include "gfxPrefs.h"
 #include "nsISupportsPrimitives.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/dom/SVGSVGElement.h"
@@ -2073,7 +2071,7 @@ nsDocument::RemoveDocStyleSheetsFromStyleSets()
     if (sheet->IsApplicable()) {
       nsCOMPtr<nsIPresShell> shell = GetShell();
       if (shell) {
-        shell->StyleSet()->RemoveDocStyleSheet(sheet);
+        shell->StyleSet()->RemoveDocStyleSheet(sheet->AsGecko());
       }
     }
     // XXX Tell observers?
@@ -2092,7 +2090,7 @@ nsDocument::RemoveStyleSheetsFromStyleSets(
     if (sheet->IsApplicable()) {
       nsCOMPtr<nsIPresShell> shell = GetShell();
       if (shell) {
-        shell->StyleSet()->RemoveStyleSheet(aType, sheet);
+        shell->StyleSet()->RemoveStyleSheet(aType, sheet->AsGecko());
       }
     }
     // XXX Tell observers?
@@ -2158,18 +2156,18 @@ nsDocument::ResetStylesheetsToURI(nsIURI* aURI)
 }
 
 static void
-AppendSheetsToStyleSet(StyleSetHandle aStyleSet,
+AppendSheetsToStyleSet(nsStyleSet* aStyleSet,
                        const nsTArray<RefPtr<StyleSheet>>& aSheets,
                        SheetType aType)
 {
   for (StyleSheet* sheet : Reversed(aSheets)) {
-    aStyleSet->AppendStyleSheet(aType, sheet);
+    aStyleSet->AppendStyleSheet(aType, sheet->AsGecko());
   }
 }
 
 
 void
-nsDocument::FillStyleSet(StyleSetHandle aStyleSet)
+nsDocument::FillStyleSet(nsStyleSet* aStyleSet)
 {
   NS_PRECONDITION(aStyleSet, "Must have a style set");
   NS_PRECONDITION(aStyleSet->SheetCount(SheetType::Doc) == 0,
@@ -2179,21 +2177,21 @@ nsDocument::FillStyleSet(StyleSetHandle aStyleSet)
 
   for (StyleSheet* sheet : Reversed(mStyleSheets)) {
     if (sheet->IsApplicable()) {
-      aStyleSet->AddDocStyleSheet(sheet, this);
+      aStyleSet->AddDocStyleSheet(sheet->AsGecko(), this);
     }
   }
 
   nsStyleSheetService *sheetService = nsStyleSheetService::GetInstance();
   if (sheetService) {
     for (StyleSheet* sheet : *sheetService->AuthorStyleSheets()) {
-      aStyleSet->AppendStyleSheet(SheetType::Doc, sheet);
+      aStyleSet->AppendStyleSheet(SheetType::Doc, sheet->AsGecko());
     }
   }
 
   // Iterate backwards to maintain order
   for (StyleSheet* sheet : Reversed(mOnDemandBuiltInUASheets)) {
     if (sheet->IsApplicable()) {
-      aStyleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      aStyleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
   }
 
@@ -3431,7 +3429,7 @@ nsDocument::TryChannelCharset(nsIChannel *aChannel,
 
 already_AddRefed<nsIPresShell>
 nsDocument::CreateShell(nsPresContext* aContext, nsViewManager* aViewManager,
-                        StyleSetHandle aStyleSet)
+                        nsStyleSet* aStyleSet)
 {
   // Don't add anything here.  Add it to |doCreateShell| instead.
   // This exists so that subclasses can pass other values for the 4th
@@ -3441,7 +3439,7 @@ nsDocument::CreateShell(nsPresContext* aContext, nsViewManager* aViewManager,
 
 already_AddRefed<nsIPresShell>
 nsDocument::doCreateShell(nsPresContext* aContext,
-                          nsViewManager* aViewManager, StyleSetHandle aStyleSet)
+                          nsViewManager* aViewManager, nsStyleSet* aStyleSet)
 {
   NS_ASSERTION(!mPresShell, "We have a presshell already!");
 
@@ -3809,7 +3807,7 @@ nsDocument::AddOnDemandBuiltInUASheet(StyleSheet* aSheet)
       // do not override Firefox OS/Mobile's content.css sheet. Maybe we should
       // have an insertion point to match the order of
       // nsDocumentViewer::CreateStyleSet though?
-      shell->StyleSet()->PrependStyleSheet(SheetType::Agent, aSheet);
+      shell->StyleSet()->PrependStyleSheet(SheetType::Agent, aSheet->AsGecko());
     }
   }
 
@@ -3821,7 +3819,7 @@ nsDocument::AddStyleSheetToStyleSets(StyleSheet* aSheet)
 {
   nsCOMPtr<nsIPresShell> shell = GetShell();
   if (shell) {
-    shell->StyleSet()->AddDocStyleSheet(aSheet, this);
+    shell->StyleSet()->AddDocStyleSheet(aSheet->AsGecko(), this);
   }
 }
 
@@ -3888,7 +3886,7 @@ nsDocument::RemoveStyleSheetFromStyleSets(StyleSheet* aSheet)
 {
   nsCOMPtr<nsIPresShell> shell = GetShell();
   if (shell) {
-    shell->StyleSet()->RemoveDocStyleSheet(aSheet);
+    shell->StyleSet()->RemoveDocStyleSheet(aSheet->AsGecko());
   }
 }
 
@@ -4104,7 +4102,7 @@ nsDocument::AddAdditionalStyleSheet(additionalSheetType aType, StyleSheet* aShee
   nsCOMPtr<nsIPresShell> shell = GetShell();
   if (shell) {
     SheetType type = ConvertAdditionalSheetType(aType);
-    shell->StyleSet()->AppendStyleSheet(type, aSheet);
+    shell->StyleSet()->AppendStyleSheet(type, aSheet->AsGecko());
   }
 
   // Passing false, so documet.styleSheets.length will not be affected by
@@ -4132,7 +4130,7 @@ nsDocument::RemoveAdditionalStyleSheet(additionalSheetType aType, nsIURI* aSheet
       nsCOMPtr<nsIPresShell> shell = GetShell();
       if (shell) {
         SheetType type = ConvertAdditionalSheetType(aType);
-        shell->StyleSet()->RemoveStyleSheet(type, sheetRef);
+        shell->StyleSet()->RemoveStyleSheet(type, sheetRef->AsGecko());
       }
     }
 
@@ -12157,7 +12155,7 @@ nsIDocument::FlushUserFontSet()
       nsTArray<nsFontFaceRuleContainer> rules;
       nsIPresShell* shell = GetShell();
       if (shell) {
-        if (!shell->StyleSet()->AsGecko()->AppendFontFaceRules(rules)) {
+        if (!shell->StyleSet()->AppendFontFaceRules(rules)) {
           return;
         }
       }
diff --git a/dom/base/nsDocument.h b/dom/base/nsDocument.h
index 923fb49ae9..22157500a0 100644
--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -43,7 +43,7 @@
 #include "nsGkAtoms.h"
 #include "nsIApplicationCache.h"
 #include "nsIApplicationCacheContainer.h"
-#include "mozilla/StyleSetHandle.h"
+#include "nsStyleSet.h"
 #include "PLDHashTable.h"
 #include "nsAttrAndChildArray.h"
 #include "nsDOMAttributeMap.h"
@@ -426,7 +426,7 @@ public:
   virtual already_AddRefed<nsIPresShell> CreateShell(
       nsPresContext* aContext,
       nsViewManager* aViewManager,
-      mozilla::StyleSetHandle aStyleSet) override;
+      nsStyleSet* aStyleSet) override;
   virtual void DeleteShell() override;
 
   virtual nsresult GetAllowPlugins(bool* aAllowPlugins) override;
@@ -1113,14 +1113,14 @@ public:
 protected:
   already_AddRefed<nsIPresShell> doCreateShell(nsPresContext* aContext,
                                                nsViewManager* aViewManager,
-                                               mozilla::StyleSetHandle aStyleSet);
+                                               nsStyleSet* aStyleSet);
 
   void RemoveDocStyleSheetsFromStyleSets();
   void RemoveStyleSheetsFromStyleSets(
       const nsTArray<RefPtr<mozilla::StyleSheet>>& aSheets,
       mozilla::SheetType aType);
   void ResetStylesheetsToURI(nsIURI* aURI);
-  void FillStyleSet(mozilla::StyleSetHandle aStyleSet);
+  void FillStyleSet(nsStyleSet* aStyleSet);
 
   // Return whether all the presshells for this document are safe to flush
   bool IsSafeToFlush() const;
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index b7e67600c5..90c0668e2e 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -96,6 +96,7 @@ class nsWindowSizes;
 class nsDOMCaretPosition;
 class nsViewportInfo;
 class nsIGlobalObject;
+class nsStyleSet;
 struct nsCSSSelectorList;
 
 namespace mozilla {
@@ -103,7 +104,6 @@ class CSSStyleSheet;
 class ErrorResult;
 class EventStates;
 class PendingAnimationTracker;
-class StyleSetHandle;
 class SVGAttrAnimationRuleProcessor;
 template<typename> class OwningNonNull;
 
@@ -781,7 +781,7 @@ public:
   virtual already_AddRefed<nsIPresShell> CreateShell(
       nsPresContext* aContext,
       nsViewManager* aViewManager,
-      mozilla::StyleSetHandle aStyleSet) = 0;
+      nsStyleSet* aStyleSet) = 0;
   virtual void DeleteShell() = 0;
 
   nsIPresShell* GetShell() const
diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index 0314664343..a7d937fd3c 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -121,8 +121,7 @@
 #include "nsFontMetrics.h"
 #include "Units.h"
 #include "CanvasUtils.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "mozilla/layers/CanvasClient.h"
 
 #undef free // apparently defined by some windows header, clashing with a free()
@@ -2670,7 +2669,7 @@ GetFontParentStyleContext(Element* aElement, nsIPresShell* aPresShell,
 
   // otherwise inherit from default (10px sans-serif)
 
-  nsStyleSet* styleSet = aPresShell->StyleSet()->GetAsGecko();
+  nsStyleSet* styleSet = aPresShell->StyleSet();
   if (!styleSet) {
     aError.Throw(NS_ERROR_FAILURE);
     return nullptr;
@@ -2711,7 +2710,7 @@ GetFontStyleContext(Element* aElement, const nsAString& aFont,
                     nsAString& aOutUsedFont,
                     ErrorResult& aError)
 {
-  nsStyleSet* styleSet = aPresShell->StyleSet()->GetAsGecko();
+  nsStyleSet* styleSet = aPresShell->StyleSet();
   if (!styleSet) {
     aError.Throw(NS_ERROR_FAILURE);
     return nullptr;
@@ -2785,7 +2784,7 @@ ResolveStyleForFilter(const nsAString& aFilterString,
                       nsStyleContext* aParentContext,
                       ErrorResult& aError)
 {
-  nsStyleSet* styleSet = aPresShell->StyleSet()->GetAsGecko();
+  nsStyleSet* styleSet = aPresShell->StyleSet();
   if (!styleSet) {
     aError.Throw(NS_ERROR_FAILURE);
     return nullptr;
diff --git a/dom/html/nsGenericHTMLElement.cpp b/dom/html/nsGenericHTMLElement.cpp
index b34f10df6e..8375c6df8e 100644
--- a/dom/html/nsGenericHTMLElement.cpp
+++ b/dom/html/nsGenericHTMLElement.cpp
@@ -103,8 +103,7 @@
 #include "mozilla/dom/HTMLBodyElement.h"
 #include "imgIContainer.h"
 #include "nsComputedDOMStyle.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "ReferrerPolicy.h"
 #include "mozilla/dom/HTMLLabelElement.h"
 
@@ -3019,7 +3018,7 @@ IsOrHasAncestorWithDisplayNone(Element* aElement, nsIPresShell* aPresShell)
     return false;
   }
 
-  StyleSetHandle styleSet = aPresShell->StyleSet();
+  nsStyleSet* styleSet = aPresShell->StyleSet();
   RefPtr<nsStyleContext> sc;
   for (int32_t i = elementsToCheck.Length() - 1; i >= 0; --i) {
     if (sc) {
diff --git a/dom/html/nsHTMLDocument.cpp b/dom/html/nsHTMLDocument.cpp
index bfce03ec63..fd8f460738 100644
--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -273,7 +273,7 @@ nsHTMLDocument::ResetToURI(nsIURI *aURI, nsILoadGroup *aLoadGroup,
 already_AddRefed<nsIPresShell>
 nsHTMLDocument::CreateShell(nsPresContext* aContext,
                             nsViewManager* aViewManager,
-                            StyleSetHandle aStyleSet)
+                            nsStyleSet* aStyleSet)
 {
   return doCreateShell(aContext, aViewManager, aStyleSet);
 }
diff --git a/dom/html/nsHTMLDocument.h b/dom/html/nsHTMLDocument.h
index 582ac8f5b2..d7e6f88429 100644
--- a/dom/html/nsHTMLDocument.h
+++ b/dom/html/nsHTMLDocument.h
@@ -55,7 +55,7 @@ public:
   virtual already_AddRefed<nsIPresShell> CreateShell(
       nsPresContext* aContext,
       nsViewManager* aViewManager,
-      mozilla::StyleSetHandle aStyleSet) override;
+      nsStyleSet* aStyleSet) override;
 
   virtual nsresult StartDocumentLoad(const char* aCommand,
                                      nsIChannel* aChannel,
diff --git a/gfx/layers/apz/util/ActiveElementManager.cpp b/gfx/layers/apz/util/ActiveElementManager.cpp
index 20d34aa2bb..a51b038d9c 100644
--- a/gfx/layers/apz/util/ActiveElementManager.cpp
+++ b/gfx/layers/apz/util/ActiveElementManager.cpp
@@ -6,8 +6,6 @@
 #include "ActiveElementManager.h"
 #include "mozilla/EventStateManager.h"
 #include "mozilla/EventStates.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "mozilla/Preferences.h"
 #include "base/message_loop.h"
 #include "base/task.h"
@@ -166,7 +164,7 @@ ElementHasActiveStyle(dom::Element* aElement)
   if (!pc) {
     return false;
   }
-  StyleSetHandle styleSet = pc->StyleSet();
+  nsStyleSet* styleSet = pc->StyleSet();
   for (dom::Element* e = aElement; e; e = e->GetParentElement()) {
     if (styleSet->HasStateDependentStyle(e, NS_EVENT_STATE_ACTIVE)) {
       AEM_LOG("Element %p's style is dependent on the active state\n", e);
diff --git a/layout/base/RestyleManager.cpp b/layout/base/RestyleManager.cpp
index 8bbbe6407b..23eaea9355 100644
--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -3869,7 +3869,7 @@ RestyleManager::ComputeAndProcessStyleChange(nsStyleContext*        aNewContext,
 nsStyleSet*
 ElementRestyler::StyleSet() const
 {
-  return mPresContext->StyleSet()->AsGecko();
+  return mPresContext->StyleSet();
 }
 
 AutoDisplayContentsAncestorPusher::AutoDisplayContentsAncestorPusher(
diff --git a/layout/base/RestyleManager.h b/layout/base/RestyleManager.h
index c20f96979d..199587d82c 100644
--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -458,7 +458,7 @@ public:
 
 private:
   inline nsStyleSet* StyleSet() const {
-    return PresContext()->StyleSet()->AsGecko();
+    return PresContext()->StyleSet();
   }
 
   /* aMinHint is the minimal change that should be made to the element */
diff --git a/layout/base/RestyleManagerBase.cpp b/layout/base/RestyleManagerBase.cpp
index 192c0df99e..94e03b9031 100644
--- a/layout/base/RestyleManagerBase.cpp
+++ b/layout/base/RestyleManagerBase.cpp
@@ -5,8 +5,7 @@
 
 #include "mozilla/RestyleManagerBase.h"
 #include "mozilla/RestyleManager.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h" // for Ptr::HasStateDependentStyle
+#include "nsStyleSet.h" // for HasStateDependentStyle
 #include "ActiveLayerTracker.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsCSSRendering.h"
@@ -52,7 +51,7 @@ RestyleManagerBase::ContentStateChangedInternal(Element* aElement,
   MOZ_ASSERT(aOutChangeHint);
   MOZ_ASSERT(aOutRestyleHint);
 
-  StyleSetHandle styleSet = PresContext()->StyleSet();
+  nsStyleSet* styleSet = PresContext()->StyleSet();
   NS_ASSERTION(styleSet, "couldn't get style set");
 
   *aOutChangeHint = nsChangeHint(0);
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index d6176bd945..e6a7c76dd8 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -34,8 +34,7 @@
 #include "nsPresShell.h"
 #include "nsIPresShell.h"
 #include "nsUnicharUtils.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsViewManager.h"
 #include "nsStyleConsts.h"
 #include "nsIDOMXULElement.h"
@@ -1837,7 +1836,7 @@ nsCSSFrameConstructor::CreateGeneratedContentItem(nsFrameConstructorState& aStat
 
   MOZ_ASSERT(aParentContent->IsElement());
 
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
 
   // Probe for the existence of the pseudo-element
   RefPtr<nsStyleContext> pseudoStyleContext;
@@ -2691,11 +2690,11 @@ nsCSSFrameConstructor::ConstructRootFrame()
 {
   AUTO_LAYOUT_PHASE_ENTRY_POINT(mPresShell->GetPresContext(), FrameC);
 
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
 
   // Set up our style rule observer.
   // XXXbz wouldn't this make more sense as part of presshell init?
-  styleSet->AsGecko()->SetBindingManager(mDocument->BindingManager());
+  styleSet->SetBindingManager(mDocument->BindingManager());
 
   // --------- BUILD VIEWPORT -----------
   RefPtr<nsStyleContext> viewportPseudoStyle =
@@ -2860,7 +2859,7 @@ nsCSSFrameConstructor::SetUpDocElementContainingBlock(nsIContent* aDocElement)
   // Start off with the viewport as parent; we'll adjust it as needed.
   nsContainerFrame* parentFrame = viewportFrame;
 
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
   // If paginated, make sure we don't put scrollbars in
   if (!isScrollable) {
     rootPseudoStyle = styleSet->ResolveAnonymousBoxStyle(rootPseudo,
@@ -2961,7 +2960,7 @@ nsCSSFrameConstructor::ConstructPageFrame(nsIPresShell*  aPresShell,
                                           nsContainerFrame*& aCanvasFrame)
 {
   nsStyleContext* parentStyleContext = aParentFrame->StyleContext();
-  StyleSetHandle styleSet = aPresShell->StyleSet();
+  nsStyleSet* styleSet = aPresShell->StyleSet();
 
   RefPtr<nsStyleContext> pagePseudoStyle;
   pagePseudoStyle = styleSet->ResolveAnonymousBoxStyle(nsCSSAnonBoxes::page,
@@ -4560,7 +4559,7 @@ nsCSSFrameConstructor::BeginBuildingScrollFrame(nsFrameConstructorState& aState,
   aNewFrame = gfxScrollFrame;
 
   // we used the style that was passed in. So resolve another one.
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
   RefPtr<nsStyleContext> scrolledChildStyle =
     styleSet->ResolveAnonymousBoxStyle(aScrolledPseudo, contentStyle);
 
@@ -5014,7 +5013,7 @@ nsCSSFrameConstructor::ResolveStyleContext(nsStyleContext* aParentStyleContext,
                                            nsFrameConstructorState* aState,
                                            Element* aOriginatingElementOrNull)
 {
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
   aContent->OwnerDoc()->FlushPendingLinkUpdates();
 
   RefPtr<nsStyleContext> result;
@@ -5096,7 +5095,7 @@ nsCSSFrameConstructor::FlushAccumulatedBlock(nsFrameConstructorState& aState,
   nsStyleContext* parentContext =
     nsFrame::CorrectStyleParentFrame(aParentFrame,
                                      anonPseudo)->StyleContext();
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
   RefPtr<nsStyleContext> blockContext;
   blockContext = styleSet->
     ResolveAnonymousBoxStyle(anonPseudo, parentContext);
@@ -11031,7 +11030,7 @@ nsCSSFrameConstructor::CreateFloatingLetterFrame(
   // get a proper style context for it (the one passed in is for the
   // letter frame and will have the float property set on it; the text
   // frame shouldn't have that set).
-  StyleSetHandle styleSet = mPresShell->StyleSet();
+  nsStyleSet* styleSet = mPresShell->StyleSet();
   RefPtr<nsStyleContext> textSC = styleSet->
     ResolveStyleForText(aTextContent, aStyleContext);
   aTextFrame->SetStyleContextWithoutNotification(textSC);
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 1068669a8a..75d42ebe04 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -19,8 +19,7 @@
 #include "nsIDocument.h"
 #include "nsPresContext.h"
 #include "nsIPresShell.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsIFrame.h"
 #include "nsIWritablePropertyBag2.h"
 #include "nsSubDocumentFrame.h"
@@ -679,12 +678,12 @@ nsDocumentViewer::InitPresentationStuff(bool aDoInitialReflow)
                "Someone should have destroyed the presshell!");
 
   // Create the style set...
-  StyleSetHandle styleSet = CreateStyleSet(mDocument);
+  nsStyleSet* styleSet = CreateStyleSet(mDocument);
 
   // Now make the shell for the document
   mPresShell = mDocument->CreateShell(mPresContext, mViewManager, styleSet);
   if (!mPresShell) {
-    styleSet->Delete();
+    delete styleSet;
     return NS_ERROR_FAILURE;
   }
 
@@ -2268,7 +2267,7 @@ nsDocumentViewer::RequestWindowClose(bool* aCanClose)
   return NS_OK;
 }
 
-StyleSetHandle
+nsStyleSet*
 nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
 {
   // Make sure this does the same thing as PresShell::AddSheet wrt ordering.
@@ -2276,7 +2275,7 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
   // this should eventually get expanded to allow for creating
   // different sets for different media
 
-  StyleSetHandle styleSet = new nsStyleSet();
+  nsStyleSet* styleSet = new nsStyleSet();
 
   styleSet->BeginUpdate();
   
@@ -2307,7 +2306,7 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
   }
 
   if (sheet)
-    styleSet->AppendStyleSheet(SheetType::User, sheet);
+    styleSet->AppendStyleSheet(SheetType::User, sheet->AsGecko());
 
   // Append chrome sheets (scrollbars + forms).
   bool shouldOverride = false;
@@ -2343,7 +2342,7 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
           cssLoader->LoadSheetSync(uri, &chromeSheet);
           if (!chromeSheet) continue;
 
-          styleSet->PrependStyleSheet(SheetType::Agent, chromeSheet);
+          styleSet->PrependStyleSheet(SheetType::Agent, chromeSheet->AsGecko());
           shouldOverride = true;
         }
         free(str);
@@ -2354,7 +2353,7 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
   if (!shouldOverride) {
     sheet = cache->ScrollbarsSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
   }
 
@@ -2370,12 +2369,12 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
 
     sheet = cache->NumberControlSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
 
     sheet = cache->FormsSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
 
     if (aDocument->LoadsFullXULStyleSheetUpFront()) {
@@ -2383,7 +2382,7 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
       // up-front here.
       sheet = cache->XULSheet();
       if (sheet) {
-        styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+        styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
       }
     }
 
@@ -2391,25 +2390,25 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
     if (sheet) {
       // Load the minimal XUL rules for scrollbars and a few other XUL things
       // that non-XUL (typically HTML) documents commonly use.
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
 
     sheet = cache->CounterStylesSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
 
     if (nsLayoutUtils::ShouldUseNoScriptSheet(aDocument)) {
       sheet = cache->NoScriptSheet();
       if (sheet) {
-        styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+        styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
       }
     }
 
     if (nsLayoutUtils::ShouldUseNoFramesSheet(aDocument)) {
       sheet = cache->NoFramesSheet();
       if (sheet) {
-        styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+        styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
       }
     }
 
@@ -2418,26 +2417,26 @@ nsDocumentViewer::CreateStyleSet(nsIDocument* aDocument)
 
     sheet = cache->HTMLSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
 
     styleSet->PrependStyleSheet(SheetType::Agent,
-                                cache->UASheet());
+                                cache->UASheet()->AsGecko());
   } else {
     // SVG documents may have scrollbars and need the scrollbar styling.
     sheet = cache->MinimalXULSheet();
     if (sheet) {
-      styleSet->PrependStyleSheet(SheetType::Agent, sheet);
+      styleSet->PrependStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
   }
 
   nsStyleSheetService* sheetService = nsStyleSheetService::GetInstance();
   if (sheetService) {
     for (StyleSheet* sheet : *sheetService->AgentStyleSheets()) {
-      styleSet->AppendStyleSheet(SheetType::Agent, sheet);
+      styleSet->AppendStyleSheet(SheetType::Agent, sheet->AsGecko());
     }
     for (StyleSheet* sheet : Reversed(*sheetService->UserStyleSheets())) {
-      styleSet->PrependStyleSheet(SheetType::User, sheet);
+      styleSet->PrependStyleSheet(SheetType::User, sheet->AsGecko());
     }
   }
 
diff --git a/layout/base/nsFrameManagerBase.h b/layout/base/nsFrameManagerBase.h
index 1f0daa7fec..2ae1ea0ed6 100644
--- a/layout/base/nsFrameManagerBase.h
+++ b/layout/base/nsFrameManagerBase.h
@@ -24,6 +24,7 @@
 
 class nsIFrame;
 class nsIPresShell;
+class nsStyleSet;
 
 class nsFrameManagerBase
 {
diff --git a/layout/base/nsIDocumentViewerPrint.h b/layout/base/nsIDocumentViewerPrint.h
index e3c397f3a3..c0d730dc00 100644
--- a/layout/base/nsIDocumentViewerPrint.h
+++ b/layout/base/nsIDocumentViewerPrint.h
@@ -8,10 +8,8 @@
 #include "nsISupports.h"
 
 class nsIDocument;
-namespace mozilla {
-class StyleSetHandle;
-} // namespace mozilla
 class nsIPresShell;
+class nsStyleSet;
 class nsPresContext;
 class nsViewManager;
 
@@ -38,7 +36,7 @@ public:
   // The style set returned by CreateStyleSet is in the middle of an
   // update batch so that the caller can add sheets to it if needed.
   // Callers should call EndUpdate() on it when ready to use.
-  virtual mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) = 0;
+  virtual nsStyleSet* CreateStyleSet(nsIDocument* aDocument) = 0;
 
   virtual void IncrementDestroyRefCount() = 0;
   virtual void DecrementDestroyRefCount() = 0;
@@ -74,7 +72,7 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsIDocumentViewerPrint,
   bool GetIsPrinting() override; \
   void SetIsPrintPreview(bool aIsPrintPreview) override; \
   bool GetIsPrintPreview() override; \
-  mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) override; \
+  nsStyleSet* CreateStyleSet(nsIDocument* aDocument) override; \
   void IncrementDestroyRefCount() override; \
   void DecrementDestroyRefCount() override; \
   void ReturnToGalleyPresentation() override; \
diff --git a/layout/base/nsIPresShell.h b/layout/base/nsIPresShell.h
index cf19867ef0..5ae95d5825 100644
--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -24,7 +24,6 @@
 #include "mozilla/EventForwards.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StaticPtr.h"
-#include "mozilla/StyleSetHandle.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/WeakPtr.h"
 #include "gfxPoint.h"
@@ -62,6 +61,7 @@ class nsIPageSequenceFrame;
 class nsCanvasFrame;
 class nsAString;
 class nsCaret;
+class nsStyleSet;
 namespace mozilla {
 class AccessibleCaretEventHub;
 class CSSStyleSheet;
@@ -323,7 +323,7 @@ public:
 #endif
 
 #ifdef MOZILLA_INTERNAL_API
-  mozilla::StyleSetHandle StyleSet() const { return mStyleSet; }
+  nsStyleSet* StyleSet() const { return mStyleSet; }
 
   nsCSSFrameConstructor* FrameConstructor() const { return mFrameConstructor; }
 
@@ -1722,7 +1722,7 @@ protected:
   // we must share ownership.
   nsCOMPtr<nsIDocument>     mDocument;
   RefPtr<nsPresContext>   mPresContext;
-  mozilla::StyleSetHandle   mStyleSet;      // [OWNS]
+  nsStyleSet*               mStyleSet;      // [OWNS]
   nsCSSFrameConstructor*    mFrameConstructor; // [OWNS]
   nsViewManager*           mViewManager;   // [WEAK] docViewer owns it so I don't have to
   nsPresArena               mFrameArena;
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 88b109e6da..d1baeb0d1c 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -114,8 +114,7 @@
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventStateManager.h"
 #include "mozilla/RuleNodeCacheConditions.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "RegionBuilder.h"
 #include "SVGSVGElement.h"
 #include "nsDocument.h"
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index 785b54bbc7..f473619537 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -18,8 +18,7 @@
 #include "nsDocShell.h"
 #include "nsIContentViewer.h"
 #include "nsPIDOMWindow.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsIContent.h"
 #include "nsIFrame.h"
 #include "nsIDocument.h"
@@ -1142,18 +1141,18 @@ nsPresContext::CompatibilityModeChanged()
     return;
   }
 
-  StyleSetHandle styleSet = mShell->StyleSet();
+  nsStyleSet* styleSet = mShell->StyleSet();
   auto cache = nsLayoutStylesheetCache::Get();
   StyleSheet* sheet = cache->QuirkSheet();
 
   if (needsQuirkSheet) {
     // quirk.css needs to come after html.css; we just keep it at the end.
     DebugOnly<nsresult> rv =
-      styleSet->AppendStyleSheet(SheetType::Agent, sheet);
+      styleSet->AppendStyleSheet(SheetType::Agent, sheet->AsGecko());
     NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "failed to insert quirk.css");
   } else {
     DebugOnly<nsresult> rv =
-      styleSet->RemoveStyleSheet(SheetType::Agent, sheet);
+      styleSet->RemoveStyleSheet(SheetType::Agent, sheet->AsGecko());
     NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "failed to remove quirk.css");
   }
 
@@ -1375,7 +1374,7 @@ GetPropagatedScrollStylesForViewport(nsPresContext* aPresContext,
   }
 
   // Check the style on the document root element
-  StyleSetHandle styleSet = aPresContext->StyleSet();
+  nsStyleSet* styleSet = aPresContext->StyleSet();
   RefPtr<nsStyleContext> rootStyle;
   rootStyle = styleSet->ResolveStyleFor(docElement, nullptr);
   if (CheckOverflow(rootStyle->StyleDisplay(), aStyles)) {
@@ -1882,7 +1881,7 @@ nsPresContext::MediaFeatureValuesChanged(nsRestyleHint aRestyleHint,
 
   // MediumFeaturesChanged updates the applied rules, so it always gets called.
   if (mShell) {
-    if (mShell->StyleSet()->AsGecko()->MediumFeaturesChanged()) {
+    if (mShell->StyleSet()->MediumFeaturesChanged()) {
       aRestyleHint |= eRestyle_Subtree;
     }
   }
@@ -2135,7 +2134,7 @@ nsPresContext::NotifyMissingFonts()
 void
 nsPresContext::EnsureSafeToHandOutCSSRules()
 {
-  nsStyleSet* styleSet = mShell->StyleSet()->GetAsGecko();
+  nsStyleSet* styleSet = mShell->StyleSet();
   if (!styleSet) {
     return;
   }
@@ -2475,7 +2474,7 @@ nsPresContext::HasCachedStyleData()
     return false;
   }
 
-  nsStyleSet* styleSet = mShell->StyleSet()->GetAsGecko();
+  nsStyleSet* styleSet = mShell->StyleSet();
   if (!styleSet) {
     return mShell->DidInitialize();
   }
diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index b90c96c477..d904948c86 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -229,7 +229,7 @@ public:
   }
 
 #ifdef MOZILLA_INTERNAL_API
-  mozilla::StyleSetHandle StyleSet() { return GetPresShell()->StyleSet(); }
+  nsStyleSet* StyleSet() { return GetPresShell()->StyleSet(); }
 
   nsFrameManager* FrameManager()
     { return PresShell()->FrameManager(); }
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index aba11e4c04..43a644a2b7 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -190,8 +190,6 @@
 #include "mozilla/layers/InputAPZContext.h"
 #include "mozilla/layers/ScrollInputMethods.h"
 #include "nsStyleSet.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/dom/ImageTracker.h"
@@ -848,7 +846,7 @@ PresShell::~PresShell()
 
   MOZ_ASSERT(mAllocatedPointers.IsEmpty(), "Some pres arena objects were not freed");
 
-  mStyleSet->Delete();
+  delete mStyleSet;
   delete mFrameConstructor;
 
   mCurrentEventContent = nullptr;
@@ -864,7 +862,7 @@ void
 PresShell::Init(nsIDocument* aDocument,
                 nsPresContext* aPresContext,
                 nsViewManager* aViewManager,
-                StyleSetHandle aStyleSet)
+                nsStyleSet* aStyleSet)
 {
   NS_PRECONDITION(aDocument, "null ptr");
   NS_PRECONDITION(aPresContext, "null ptr");
@@ -1400,7 +1398,7 @@ PresShell::UpdatePreferenceStyles()
 
   RemovePreferenceStyles();
 
-  mStyleSet->AppendStyleSheet(SheetType::User, newPrefSheet);
+  mStyleSet->AppendStyleSheet(SheetType::User, newPrefSheet->AsGecko());
   mPrefStyleSheet = newPrefSheet;
 
   mStyleSet->EndUpdate();
@@ -1410,7 +1408,7 @@ void
 PresShell::RemovePreferenceStyles()
 {
   if (mPrefStyleSheet) {
-    mStyleSet->RemoveStyleSheet(SheetType::User, mPrefStyleSheet);
+    mStyleSet->RemoveStyleSheet(SheetType::User, mPrefStyleSheet->AsGecko());
     mPrefStyleSheet = nullptr;
   }
 }
@@ -1433,13 +1431,13 @@ PresShell::AddUserSheet(nsISupports* aSheet)
   // Iterate forwards when removing so the searches for RemoveStyleSheet are as
   // short as possible.
   for (StyleSheet* sheet : userSheets) {
-    mStyleSet->RemoveStyleSheet(SheetType::User, sheet);
+    mStyleSet->RemoveStyleSheet(SheetType::User, sheet->AsGecko());
   }
 
   // Now iterate backwards, so that the order of userSheets will be the same as
   // the order of sheets from it in the style set.
   for (StyleSheet* sheet : Reversed(userSheets)) {
-    mStyleSet->PrependStyleSheet(SheetType::User, sheet);
+    mStyleSet->PrependStyleSheet(SheetType::User, sheet->AsGecko());
   }
 
   mStyleSet->EndUpdate();
@@ -1457,7 +1455,7 @@ PresShell::AddAgentSheet(nsISupports* aSheet)
     return;
   }
 
-  mStyleSet->AppendStyleSheet(SheetType::Agent, sheet);
+  mStyleSet->AppendStyleSheet(SheetType::Agent, sheet->AsGecko());
   RestyleForCSSRuleChanges();
 }
 
@@ -1474,9 +1472,9 @@ PresShell::AddAuthorSheet(nsISupports* aSheet)
   StyleSheet* firstAuthorSheet =
     mDocument->GetFirstAdditionalAuthorSheet();
   if (firstAuthorSheet) {
-    mStyleSet->InsertStyleSheetBefore(SheetType::Doc, sheet, firstAuthorSheet);
+    mStyleSet->InsertStyleSheetBefore(SheetType::Doc, sheet->AsGecko(), firstAuthorSheet->AsGecko());
   } else {
-    mStyleSet->AppendStyleSheet(SheetType::Doc, sheet);
+    mStyleSet->AppendStyleSheet(SheetType::Doc, sheet->AsGecko());
   }
 
   RestyleForCSSRuleChanges();
@@ -1490,7 +1488,7 @@ PresShell::RemoveSheet(SheetType aType, nsISupports* aSheet)
     return;
   }
 
-  mStyleSet->RemoveStyleSheet(aType, sheet);
+  mStyleSet->RemoveStyleSheet(aType, sheet->AsGecko());
   RestyleForCSSRuleChanges();
 }
 
@@ -4168,7 +4166,7 @@ PresShell::DocumentStatesChanged(nsIDocument* aDocument,
   NS_PRECONDITION(!mIsDocumentGone, "Unexpected DocumentStatesChanged");
   NS_PRECONDITION(aDocument == mDocument, "Unexpected aDocument");
 
-  nsStyleSet* styleSet = mStyleSet->GetAsGecko();
+  nsStyleSet* styleSet = mStyleSet;
   if (!styleSet) {
     return;
   }
@@ -8772,19 +8770,23 @@ PresShell::GetAgentStyleSheets(nsTArray<RefPtr<StyleSheet>>& aSheets)
 nsresult
 PresShell::SetAgentStyleSheets(const nsTArray<RefPtr<StyleSheet>>& aSheets)
 {
-  return mStyleSet->ReplaceSheets(SheetType::Agent, aSheets);
+  nsTArray<RefPtr<CSSStyleSheet>> newSheets(aSheets.Length());
+  for (auto& sheet : aSheets) {
+    newSheets.AppendElement(sheet->AsGecko());
+  }
+  return mStyleSet->ReplaceSheets(SheetType::Agent, newSheets);
 }
 
 nsresult
 PresShell::AddOverrideStyleSheet(StyleSheet* aSheet)
 {
-  return mStyleSet->PrependStyleSheet(SheetType::Override, aSheet);
+  return mStyleSet->PrependStyleSheet(SheetType::Override, aSheet->AsGecko());
 }
 
 nsresult
 PresShell::RemoveOverrideStyleSheet(StyleSheet* aSheet)
 {
-  return mStyleSet->RemoveStyleSheet(SheetType::Override, aSheet);
+  return mStyleSet->RemoveStyleSheet(SheetType::Override, aSheet->AsGecko());
 }
 
 static void
@@ -9957,7 +9959,7 @@ PresShell::VerifyIncrementalReflow()
 
   // Create a new presentation shell to view the document. Use the
   // exact same style information that this document has.
-  nsAutoPtr<nsStyleSet> newSet(CloneStyleSet(mStyleSet->AsGecko()));
+  nsAutoPtr<nsStyleSet> newSet(CloneStyleSet(mStyleSet));
   nsCOMPtr<nsIPresShell> sh = mDocument->CreateShell(cx, vm, newSet.get());
   NS_ENSURE_TRUE(sh, false);
   newSet.forget();
@@ -10802,7 +10804,7 @@ PresShell::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
   *aPresShellSize += mFramesToDirty.ShallowSizeOfExcludingThis(aMallocSizeOf);
   *aPresShellSize += aArenaObjectsSize->mOther;
 
-  if (nsStyleSet* styleSet = StyleSet()->GetAsGecko()) {
+  if (nsStyleSet* styleSet = StyleSet()) {
     *aStyleSetsSize += styleSet->SizeOfIncludingThis(aMallocSizeOf);
   }
 
@@ -11010,7 +11012,7 @@ nsIPresShell::HasRuleProcessorUsedByMultipleStyleSets(uint32_t aSheetType,
   }
 
   *aRetVal = false;
-  if (nsStyleSet* styleSet = mStyleSet->GetAsGecko()) {
+  if (nsStyleSet* styleSet = mStyleSet) {
     *aRetVal = styleSet->HasRuleProcessorUsedByMultipleStyleSets(type);
   }
   return NS_OK;
diff --git a/layout/base/nsPresShell.h b/layout/base/nsPresShell.h
index fbbcfc7ecd..f47711253c 100644
--- a/layout/base/nsPresShell.h
+++ b/layout/base/nsPresShell.h
@@ -34,13 +34,13 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/MemoryReporting.h"
-#include "mozilla/StyleSetHandle.h"
 #include "mozilla/UniquePtr.h"
 #include "MobileViewportManager.h"
 #include "ZoomConstraintsClient.h"
 
 class nsIDocShell;
 class nsRange;
+class nsStyleSet;
 
 struct RangePaintInfo;
 struct nsCallbackEventRequest;
@@ -100,7 +100,7 @@ public:
   static bool IsTargetIframe(nsINode* aTarget);
 
   void Init(nsIDocument* aDocument, nsPresContext* aPresContext,
-            nsViewManager* aViewManager, mozilla::StyleSetHandle aStyleSet);
+            nsViewManager* aViewManager, nsStyleSet* aStyleSet);
   virtual void Destroy() override;
   virtual void MakeZombie() override;
 
diff --git a/layout/forms/nsButtonFrameRenderer.cpp b/layout/forms/nsButtonFrameRenderer.cpp
index 5113572995..608273a539 100644
--- a/layout/forms/nsButtonFrameRenderer.cpp
+++ b/layout/forms/nsButtonFrameRenderer.cpp
@@ -8,8 +8,7 @@
 #include "nsGkAtoms.h"
 #include "nsCSSPseudoElements.h"
 #include "nsNameSpaceManager.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsDisplayList.h"
 #include "nsITheme.h"
 #include "nsFrame.h"
@@ -376,7 +375,7 @@ nsButtonFrameRenderer::ReResolveStyles(nsPresContext* aPresContext)
 {
   // get all the styles
   nsStyleContext* context = mFrame->StyleContext();
-  StyleSetHandle styleSet = aPresContext->StyleSet();
+  nsStyleSet* styleSet = aPresContext->StyleSet();
 
 #ifdef DEBUG
   if (mInnerFocusStyle) {
diff --git a/layout/forms/nsColorControlFrame.cpp b/layout/forms/nsColorControlFrame.cpp
index 63aee814aa..2ba410c31f 100644
--- a/layout/forms/nsColorControlFrame.cpp
+++ b/layout/forms/nsColorControlFrame.cpp
@@ -14,8 +14,7 @@
 #include "nsIDOMHTMLInputElement.h"
 #include "nsIDOMNode.h"
 #include "nsIFormControl.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsIDocument.h"
 
 using mozilla::dom::Element;
diff --git a/layout/forms/nsComboboxControlFrame.cpp b/layout/forms/nsComboboxControlFrame.cpp
index 2d0395d7a1..e6b2de334d 100644
--- a/layout/forms/nsComboboxControlFrame.cpp
+++ b/layout/forms/nsComboboxControlFrame.cpp
@@ -30,8 +30,7 @@
 #include "nsIDocument.h"
 #include "nsIScrollableFrame.h"
 #include "nsListControlFrame.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsNodeInfoManager.h"
 #include "nsContentCreatorFunctions.h"
 #include "nsLayoutUtils.h"
@@ -1358,7 +1357,7 @@ nsComboboxControlFrame::CreateFrameForDisplayNode()
 
   // Get PresShell
   nsIPresShell *shell = PresContext()->PresShell();
-  StyleSetHandle styleSet = shell->StyleSet();
+  nsStyleSet* styleSet = shell->StyleSet();
 
   // create the style contexts for the anonymous block frame and text frame
   RefPtr<nsStyleContext> styleContext;
diff --git a/layout/forms/nsGfxButtonControlFrame.cpp b/layout/forms/nsGfxButtonControlFrame.cpp
index 768abbc21d..fd125896c7 100644
--- a/layout/forms/nsGfxButtonControlFrame.cpp
+++ b/layout/forms/nsGfxButtonControlFrame.cpp
@@ -6,8 +6,7 @@
 #include "nsGfxButtonControlFrame.h"
 #include "nsIFormControl.h"
 #include "nsGkAtoms.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsContentUtils.h"
 // MouseEvent suppression in PP
 #include "nsContentList.h"
diff --git a/layout/forms/nsMeterFrame.cpp b/layout/forms/nsMeterFrame.cpp
index e90bbb4667..4d040f5c29 100644
--- a/layout/forms/nsMeterFrame.cpp
+++ b/layout/forms/nsMeterFrame.cpp
@@ -21,8 +21,6 @@
 #include "nsContentList.h"
 #include "nsCSSPseudoElements.h"
 #include "nsStyleSet.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "nsThemeConstants.h"
 #include <algorithm>
 
diff --git a/layout/forms/nsNumberControlFrame.cpp b/layout/forms/nsNumberControlFrame.cpp
index 3e625d39af..1bae906b16 100644
--- a/layout/forms/nsNumberControlFrame.cpp
+++ b/layout/forms/nsNumberControlFrame.cpp
@@ -22,8 +22,6 @@
 #include "nsContentList.h"
 #include "nsCSSPseudoElements.h"
 #include "nsStyleSet.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "nsIDOMMutationEvent.h"
 #include "nsThreadUtils.h"
 #include "mozilla/FloatingPoint.h"
diff --git a/layout/forms/nsProgressFrame.cpp b/layout/forms/nsProgressFrame.cpp
index c734787d24..1cd10da66d 100644
--- a/layout/forms/nsProgressFrame.cpp
+++ b/layout/forms/nsProgressFrame.cpp
@@ -21,8 +21,6 @@
 #include "nsContentList.h"
 #include "nsCSSPseudoElements.h"
 #include "nsStyleSet.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "nsThemeConstants.h"
 #include <algorithm>
 
diff --git a/layout/forms/nsRangeFrame.cpp b/layout/forms/nsRangeFrame.cpp
index 7ed05a21c4..6d60372463 100644
--- a/layout/forms/nsRangeFrame.cpp
+++ b/layout/forms/nsRangeFrame.cpp
@@ -24,8 +24,7 @@
 #include "nsNodeInfoManager.h"
 #include "nsRenderingContext.h"
 #include "mozilla/dom/Element.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsThemeConstants.h"
 
 #ifdef ACCESSIBILITY
@@ -84,7 +83,7 @@ nsRangeFrame::Init(nsIContent*       aContent,
   }
   aContent->AddEventListener(NS_LITERAL_STRING("touchstart"), mDummyTouchListener, false);
 
-  StyleSetHandle styleSet = PresContext()->StyleSet();
+  nsStyleSet* styleSet = PresContext()->StyleSet();
 
   mOuterFocusStyle =
     styleSet->ProbePseudoElementStyle(aContent->AsElement(),
diff --git a/layout/forms/nsTextControlFrame.cpp b/layout/forms/nsTextControlFrame.cpp
index fd89ad075e..ad1af13221 100644
--- a/layout/forms/nsTextControlFrame.cpp
+++ b/layout/forms/nsTextControlFrame.cpp
@@ -44,8 +44,7 @@
 #include "mozilla/TextEditRules.h"
 #include "nsContentUtils.h"
 #include "nsTextNode.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "mozilla/dom/HTMLInputElement.h"
 #include "mozilla/dom/HTMLTextAreaElement.h"
 #include "mozilla/dom/ScriptSettings.h"
diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index f4e63cfea4..c0247f0b99 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -53,8 +53,7 @@
 #include "nsISelection.h"
 #include "mozilla/dom/HTMLDetailsElement.h"
 #include "mozilla/dom/HTMLSummaryElement.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 
 #include "nsBidiPresUtils.h"
 
diff --git a/layout/generic/nsFirstLetterFrame.cpp b/layout/generic/nsFirstLetterFrame.cpp
index a038c48694..f436245929 100644
--- a/layout/generic/nsFirstLetterFrame.cpp
+++ b/layout/generic/nsFirstLetterFrame.cpp
@@ -11,8 +11,7 @@
 #include "nsIContent.h"
 #include "nsLineLayout.h"
 #include "nsGkAtoms.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsFrameManager.h"
 #include "mozilla/RestyleManagerHandle.h"
 #include "mozilla/RestyleManagerHandleInlines.h"
diff --git a/layout/generic/nsFrameSetFrame.cpp b/layout/generic/nsFrameSetFrame.cpp
index 01d9f78154..73a59ae739 100644
--- a/layout/generic/nsFrameSetFrame.cpp
+++ b/layout/generic/nsFrameSetFrame.cpp
@@ -29,8 +29,7 @@
 #include "nsIDOMMutationEvent.h"
 #include "nsNameSpaceManager.h"
 #include "nsCSSAnonBoxes.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "mozilla/dom/Element.h"
 #include "nsDisplayList.h"
 #include "nsNodeUtils.h"
@@ -802,7 +801,7 @@ nsHTMLFramesetFrame::Reflow(nsPresContext*           aPresContext,
   DO_GLOBAL_REFLOW_COUNT("nsHTMLFramesetFrame");
   DISPLAY_REFLOW(aPresContext, this, aReflowInput, aDesiredSize, aStatus);
   nsIPresShell *shell = aPresContext->PresShell();
-  StyleSetHandle styleSet = shell->StyleSet();
+  nsStyleSet* styleSet = shell->StyleSet();
 
   GetParent()->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
 
diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index d6f47f2e42..6afdeef618 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -71,8 +71,7 @@
 #include "gfxRect.h"
 #include "ImageLayers.h"
 #include "ImageContainer.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsBlockFrame.h"
 #include "nsStyleStructInlines.h"
 
diff --git a/layout/generic/nsInlineFrame.cpp b/layout/generic/nsInlineFrame.cpp
index 8f24af73c1..c15e33cb6c 100644
--- a/layout/generic/nsInlineFrame.cpp
+++ b/layout/generic/nsInlineFrame.cpp
@@ -19,8 +19,7 @@
 #include "nsDisplayList.h"
 #include "mozilla/Likely.h"
 #include "SVGTextFrame.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 
 #ifdef DEBUG
 #undef NOISY_PUSHING
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 7e73692c42..a07fb749a9 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -63,8 +63,7 @@
 #include "nsIWordBreaker.h"
 #include "nsGenericDOMDataNode.h"
 #include "nsIFrameInlines.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 
 #include <algorithm>
 #include <limits>
diff --git a/layout/inspector/inDOMUtils.cpp b/layout/inspector/inDOMUtils.cpp
index f60cfd073f..5e0cb208a8 100644
--- a/layout/inspector/inDOMUtils.cpp
+++ b/layout/inspector/inDOMUtils.cpp
@@ -48,8 +48,7 @@
 #include "nsCSSProps.h"
 #include "nsCSSValue.h"
 #include "nsColor.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsStyleUtil.h"
 #include "nsQueryObject.h"
 
@@ -87,7 +86,7 @@ inDOMUtils::GetAllStyleSheets(nsIDOMDocument *aDocument, uint32_t *aLength,
   nsIPresShell* presShell = document->GetShell();
 
   if (presShell) {
-    StyleSetHandle styleSet = presShell->StyleSet();
+    nsStyleSet* styleSet = presShell->StyleSet();
     SheetType sheetType = SheetType::Agent;
     for (int32_t i = 0; i < styleSet->SheetCount(sheetType); i++) {
       sheets.AppendElement(styleSet->StyleSheetAt(sheetType, i));
@@ -97,7 +96,7 @@ inDOMUtils::GetAllStyleSheets(nsIDOMDocument *aDocument, uint32_t *aLength,
       sheets.AppendElement(styleSet->StyleSheetAt(sheetType, i));
     }
     AutoTArray<CSSStyleSheet*, 32> xblSheetArray;
-    styleSet->AsGecko()->AppendAllXBLStyleSheets(xblSheetArray);
+    styleSet->AppendAllXBLStyleSheets(xblSheetArray);
 
     // The XBL stylesheet array will quite often be full of duplicates. Cope:
     nsTHashtable<nsPtrHashKey<CSSStyleSheet>> sheetSet;
diff --git a/layout/mathml/nsMathMLFrame.cpp b/layout/mathml/nsMathMLFrame.cpp
index acb69e3879..680a64dd55 100644
--- a/layout/mathml/nsMathMLFrame.cpp
+++ b/layout/mathml/nsMathMLFrame.cpp
@@ -15,8 +15,7 @@
 #include "gfxMathTable.h"
 
 // used to map attributes into CSS rules
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsDisplayList.h"
 #include "nsRenderingContext.h"
 
diff --git a/layout/printing/nsPrintEngine.cpp b/layout/printing/nsPrintEngine.cpp
index d232b669bb..e17e0b8a08 100644
--- a/layout/printing/nsPrintEngine.cpp
+++ b/layout/printing/nsPrintEngine.cpp
@@ -125,8 +125,7 @@ static const char kPrintingPromptService[] = "@mozilla.org/embedcomp/printingpro
 #include "nsIChannel.h"
 #include "xpcpublic.h"
 #include "nsVariant.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -2239,12 +2238,12 @@ nsPrintEngine::ReflowPrintObject(nsPrintObject * aPO)
   rv = aPO->mViewManager->Init(printData->mPrintDC);
   NS_ENSURE_SUCCESS(rv,rv);
 
-  StyleSetHandle styleSet = mDocViewerPrint->CreateStyleSet(aPO->mDocument);
+  nsStyleSet* styleSet = mDocViewerPrint->CreateStyleSet(aPO->mDocument);
 
   aPO->mPresShell = aPO->mDocument->CreateShell(aPO->mPresContext,
                                                 aPO->mViewManager, styleSet);
   if (!aPO->mPresShell) {
-    styleSet->Delete();
+    delete styleSet;
     return NS_ERROR_FAILURE;
   }
 
diff --git a/layout/style/CounterStyleManager.cpp b/layout/style/CounterStyleManager.cpp
index 46bd866569..dedf017834 100644
--- a/layout/style/CounterStyleManager.cpp
+++ b/layout/style/CounterStyleManager.cpp
@@ -17,8 +17,7 @@
 #include "nsTArray.h"
 #include "nsTHashtable.h"
 #include "nsUnicodeProperties.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 
 namespace mozilla {
 
@@ -2028,9 +2027,9 @@ CounterStyleManager::BuildCounterStyle(const nsSubstring& aName)
 
   // It is intentional that the predefined names are case-insensitive
   // but the user-defined names case-sensitive.
-  StyleSetHandle styleSet = mPresContext->StyleSet();
+  nsStyleSet* styleSet = mPresContext->StyleSet();
   nsCSSCounterStyleRule* rule =
-    styleSet->AsGecko()->CounterStyleRuleForName(aName);
+    styleSet->CounterStyleRuleForName(aName);
   if (rule) {
     data = new (mPresContext) CustomCounterStyle(aName, this, rule);
   } else {
@@ -2070,9 +2069,9 @@ CounterStyleManager::NotifyRuleChanged()
     RefPtr<CounterStyle>& style = iter.Data();
     bool toBeUpdated = false;
     bool toBeRemoved = false;
-    StyleSetHandle styleSet = mPresContext->StyleSet();
+    nsStyleSet* styleSet = mPresContext->StyleSet();
     nsCSSCounterStyleRule* newRule =
-        styleSet->AsGecko()->CounterStyleRuleForName(iter.Key());
+        styleSet->CounterStyleRuleForName(iter.Key());
     if (!newRule) {
       if (style->IsCustomStyle()) {
         toBeRemoved = true;
diff --git a/layout/style/StyleAnimationValue.cpp b/layout/style/StyleAnimationValue.cpp
index 2f40533970..1a46ef7592 100644
--- a/layout/style/StyleAnimationValue.cpp
+++ b/layout/style/StyleAnimationValue.cpp
@@ -3261,7 +3261,7 @@ ComputeValuesFromStyleRule(nsCSSPropertyID aProperty,
     return false;
   }
 
-  nsStyleSet* styleSet = aStyleContext->PresContext()->StyleSet()->AsGecko();
+  nsStyleSet* styleSet = aStyleContext->PresContext()->StyleSet();
 
   RefPtr<nsStyleContext> tmpStyleContext;
   if (aIsContextSensitive) {
diff --git a/layout/style/StyleSetHandle.h b/layout/style/StyleSetHandle.h
deleted file mode 100644
index 6d17c71605..0000000000
--- a/layout/style/StyleSetHandle.h
+++ /dev/null
@@ -1,162 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_StyleSetHandle_h
-#define mozilla_StyleSetHandle_h
-
-#include "mozilla/EventStates.h"
-#include "mozilla/RefPtr.h"
-#include "mozilla/SheetType.h"
-#include "mozilla/StyleSheet.h"
-#include "nsChangeHint.h"
-#include "nsCSSPseudoElements.h"
-#include "nsTArray.h"
-
-namespace mozilla {
-class CSSStyleSheet;
-namespace dom {
-class Element;
-} // namespace dom
-} // namespace mozilla
-class nsIAtom;
-class nsIContent;
-class nsIDocument;
-class nsStyleContext;
-class nsStyleSet;
-class nsPresContext;
-struct TreeMatchContext;
-
-namespace mozilla {
-
-/**
- * Smart pointer class that can hold a pointer to an nsStyleSet.
- */
-class StyleSetHandle
-{
-public:
-  // We define this Ptr class with a StyleSet API that forwards on to the
-  // wrapped pointer, rather than putting these methods on StyleSetHandle
-  // itself, so that we can have StyleSetHandle behave like a smart pointer and
-  // be dereferenced with operator->.
-  class Ptr
-  {
-  public:
-    friend class ::mozilla::StyleSetHandle;
-
-    nsStyleSet* AsGecko()
-    {
-      return reinterpret_cast<nsStyleSet*>(mValue);
-    }
-
-    nsStyleSet* GetAsGecko() { return AsGecko(); }
-
-    const nsStyleSet* AsGecko() const
-    {
-      return const_cast<Ptr*>(this)->AsGecko();
-    }
-
-    const nsStyleSet* GetAsGecko() const { return AsGecko(); }
-
-    // These inline methods are defined in StyleSetHandleInlines.h.
-    inline void Delete();
-
-    // Style set interface.  These inline methods are defined in
-    // StyleSetHandleInlines.h and just forward to the underlying
-    // nsStyleSet.  See corresponding comments in nsStyleSet.h for
-    // descriptions of these methods.
-
-    inline void Init(nsPresContext* aPresContext);
-    inline void BeginShutdown();
-    inline void Shutdown();
-    inline bool GetAuthorStyleDisabled() const;
-    inline nsresult SetAuthorStyleDisabled(bool aStyleDisabled);
-    inline void BeginUpdate();
-    inline nsresult EndUpdate();
-    inline already_AddRefed<nsStyleContext>
-    ResolveStyleFor(dom::Element* aElement,
-                    nsStyleContext* aParentContext);
-    inline already_AddRefed<nsStyleContext>
-    ResolveStyleFor(dom::Element* aElement,
-                    nsStyleContext* aParentContext,
-                    TreeMatchContext& aTreeMatchContext);
-    inline already_AddRefed<nsStyleContext>
-    ResolveStyleForText(nsIContent* aTextNode,
-                        nsStyleContext* aParentContext);
-    inline already_AddRefed<nsStyleContext>
-    ResolveStyleForOtherNonElement(nsStyleContext* aParentContext);
-    inline already_AddRefed<nsStyleContext>
-    ResolvePseudoElementStyle(dom::Element* aParentElement,
-                              mozilla::CSSPseudoElementType aType,
-                              nsStyleContext* aParentContext,
-                              dom::Element* aPseudoElement);
-    inline already_AddRefed<nsStyleContext>
-    ResolveAnonymousBoxStyle(nsIAtom* aPseudoTag, nsStyleContext* aParentContext,
-                             uint32_t aFlags = 0);
-    inline nsresult AppendStyleSheet(SheetType aType, StyleSheet* aSheet);
-    inline nsresult PrependStyleSheet(SheetType aType, StyleSheet* aSheet);
-    inline nsresult RemoveStyleSheet(SheetType aType, StyleSheet* aSheet);
-    inline nsresult ReplaceSheets(SheetType aType,
-                           const nsTArray<RefPtr<StyleSheet>>& aNewSheets);
-    inline nsresult InsertStyleSheetBefore(SheetType aType,
-                                    StyleSheet* aNewSheet,
-                                    StyleSheet* aReferenceSheet);
-    inline int32_t SheetCount(SheetType aType) const;
-    inline StyleSheet* StyleSheetAt(SheetType aType, int32_t aIndex) const;
-    inline nsresult RemoveDocStyleSheet(StyleSheet* aSheet);
-    inline nsresult AddDocStyleSheet(StyleSheet* aSheet, nsIDocument* aDocument);
-    inline already_AddRefed<nsStyleContext>
-    ProbePseudoElementStyle(dom::Element* aParentElement,
-                            mozilla::CSSPseudoElementType aType,
-                            nsStyleContext* aParentContext);
-    inline already_AddRefed<nsStyleContext>
-    ProbePseudoElementStyle(dom::Element* aParentElement,
-                            mozilla::CSSPseudoElementType aType,
-                            nsStyleContext* aParentContext,
-                            TreeMatchContext& aTreeMatchContext,
-                            dom::Element* aPseudoElement = nullptr);
-    inline nsRestyleHint HasStateDependentStyle(dom::Element* aElement,
-                                                EventStates aStateMask);
-    inline nsRestyleHint HasStateDependentStyle(
-        dom::Element* aElement,
-        mozilla::CSSPseudoElementType aPseudoType,
-        dom::Element* aPseudoElement,
-        EventStates aStateMask);
-
-    inline void RootStyleContextAdded();
-    inline void RootStyleContextRemoved();
-
-  private:
-    // Stores a pointer to an nsStyleSet.  The least
-    // significant bit is 0 for the former, 1 for the latter.  This is
-    // valid as the least significant bit will never be used for a pointer
-    // value on platforms we care about.
-    uintptr_t mValue;
-  };
-
-  StyleSetHandle() { mPtr.mValue = 0; }
-  StyleSetHandle(const StyleSetHandle& aOth) { mPtr.mValue = aOth.mPtr.mValue; }
-  MOZ_IMPLICIT StyleSetHandle(nsStyleSet* aSet) { *this = aSet; }
-
-  StyleSetHandle& operator=(nsStyleSet* aStyleSet)
-  {
-    mPtr.mValue = reinterpret_cast<uintptr_t>(aStyleSet);
-    return *this;
-  }
-
-  // Make StyleSetHandle usable in boolean contexts.
-  explicit operator bool() const { return !!mPtr.mValue; }
-  bool operator!() const { return !mPtr.mValue; }
-
-  // Make StyleSetHandle behave like a smart pointer.
-  Ptr* operator->() { return &mPtr; }
-  const Ptr* operator->() const { return &mPtr; }
-
-private:
-  Ptr mPtr;
-};
-
-} // namespace mozilla
-
-#endif // mozilla_StyleSetHandle_h
diff --git a/layout/style/StyleSetHandleInlines.h b/layout/style/StyleSetHandleInlines.h
deleted file mode 100644
index f99842f822..0000000000
--- a/layout/style/StyleSetHandleInlines.h
+++ /dev/null
@@ -1,226 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_StyleSetHandleInlines_h
-#define mozilla_StyleSetHandleInlines_h
-
-#include "mozilla/StyleSheetInlines.h"
-#include "nsStyleSet.h"
-
-namespace mozilla {
-
-void
-StyleSetHandle::Ptr::Delete()
-{
-  if (mValue) {
-    delete AsGecko();
-  }
-}
-
-void
-StyleSetHandle::Ptr::Init(nsPresContext* aPresContext)
-{
-  AsGecko()->Init(aPresContext);
-}
-
-void
-StyleSetHandle::Ptr::BeginShutdown()
-{
-  AsGecko()->BeginShutdown();
-}
-
-void
-StyleSetHandle::Ptr::Shutdown()
-{
-  AsGecko()->Shutdown();
-}
-
-bool
-StyleSetHandle::Ptr::GetAuthorStyleDisabled() const
-{
-  return AsGecko()->GetAuthorStyleDisabled();
-}
-
-nsresult
-StyleSetHandle::Ptr::SetAuthorStyleDisabled(bool aStyleDisabled)
-{
-  return AsGecko()->SetAuthorStyleDisabled(aStyleDisabled);
-}
-
-void
-StyleSetHandle::Ptr::BeginUpdate()
-{
-  AsGecko()->BeginUpdate();
-}
-
-nsresult
-StyleSetHandle::Ptr::EndUpdate()
-{
-  return AsGecko()->EndUpdate();
-}
-
-// resolve a style context
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolveStyleFor(dom::Element* aElement,
-                                     nsStyleContext* aParentContext)
-{
-  return AsGecko()->ResolveStyleFor(aElement, aParentContext);
-}
-
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolveStyleFor(dom::Element* aElement,
-                                     nsStyleContext* aParentContext,
-                                     TreeMatchContext& aTreeMatchContext)
-{
-  return AsGecko()->ResolveStyleFor(aElement, aParentContext, aTreeMatchContext);
-}
-
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolveStyleForText(nsIContent* aTextNode,
-                                         nsStyleContext* aParentContext)
-{
-  return AsGecko()->ResolveStyleForText(aTextNode, aParentContext);
-}
-
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolveStyleForOtherNonElement(nsStyleContext* aParentContext)
-{
-  return AsGecko()->ResolveStyleForOtherNonElement(aParentContext);
-}
-
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolvePseudoElementStyle(dom::Element* aParentElement,
-                                               CSSPseudoElementType aType,
-                                               nsStyleContext* aParentContext,
-                                               dom::Element* aPseudoElement)
-{
-  return AsGecko()->ResolvePseudoElementStyle(
-    aParentElement, aType, aParentContext, aPseudoElement);
-}
-
-// aFlags is an nsStyleSet flags bitfield
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ResolveAnonymousBoxStyle(nsIAtom* aPseudoTag,
-                                              nsStyleContext* aParentContext,
-                                              uint32_t aFlags)
-{
-  return AsGecko()->ResolveAnonymousBoxStyle(aPseudoTag, aParentContext, aFlags);
-}
-
-// manage the set of style sheets in the style set
-nsresult
-StyleSetHandle::Ptr::AppendStyleSheet(SheetType aType, StyleSheet* aSheet)
-{
-  return AsGecko()->AppendStyleSheet(aType, aSheet->AsGecko());
-}
-
-nsresult
-StyleSetHandle::Ptr::PrependStyleSheet(SheetType aType, StyleSheet* aSheet)
-{
-  return AsGecko()->PrependStyleSheet(aType, aSheet->AsGecko());
-}
-
-nsresult
-StyleSetHandle::Ptr::RemoveStyleSheet(SheetType aType, StyleSheet* aSheet)
-{
-  return AsGecko()->RemoveStyleSheet(aType, aSheet->AsGecko());
-}
-
-nsresult
-StyleSetHandle::Ptr::ReplaceSheets(SheetType aType,
-                       const nsTArray<RefPtr<StyleSheet>>& aNewSheets)
-{
-  nsTArray<RefPtr<CSSStyleSheet>> newSheets(aNewSheets.Length());
-  for (auto& sheet : aNewSheets) {
-    newSheets.AppendElement(sheet->AsGecko());
-  }
-  return AsGecko()->ReplaceSheets(aType, newSheets);
-}
-
-nsresult
-StyleSetHandle::Ptr::InsertStyleSheetBefore(SheetType aType,
-                                StyleSheet* aNewSheet,
-                                StyleSheet* aReferenceSheet)
-{
-  return AsGecko()->InsertStyleSheetBefore(
-    aType, aNewSheet->AsGecko(), aReferenceSheet->AsGecko());
-}
-
-int32_t
-StyleSetHandle::Ptr::SheetCount(SheetType aType) const
-{
-  return AsGecko()->SheetCount(aType);
-}
-
-StyleSheet*
-StyleSetHandle::Ptr::StyleSheetAt(SheetType aType, int32_t aIndex) const
-{
-  return AsGecko()->StyleSheetAt(aType, aIndex);
-}
-
-nsresult
-StyleSetHandle::Ptr::RemoveDocStyleSheet(StyleSheet* aSheet)
-{
-  return AsGecko()->RemoveDocStyleSheet(aSheet->AsGecko());
-}
-
-nsresult
-StyleSetHandle::Ptr::AddDocStyleSheet(StyleSheet* aSheet,
-                                      nsIDocument* aDocument)
-{
-  return AsGecko()->AddDocStyleSheet(aSheet->AsGecko(), aDocument);
-}
-
-// check whether there is ::before/::after style for an element
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ProbePseudoElementStyle(dom::Element* aParentElement,
-                                             CSSPseudoElementType aType,
-                                             nsStyleContext* aParentContext)
-{
-  return AsGecko()->ProbePseudoElementStyle(aParentElement, aType, aParentContext);
-}
-
-already_AddRefed<nsStyleContext>
-StyleSetHandle::Ptr::ProbePseudoElementStyle(dom::Element* aParentElement,
-                                             CSSPseudoElementType aType,
-                                             nsStyleContext* aParentContext,
-                                             TreeMatchContext& aTreeMatchContext,
-                                             dom::Element* aPseudoElement)
-{
-  return AsGecko()->ProbePseudoElementStyle(
-    aParentElement, aType, aParentContext, aTreeMatchContext, aPseudoElement);
-}
-
-nsRestyleHint
-StyleSetHandle::Ptr::HasStateDependentStyle(dom::Element* aElement,
-                                            EventStates aStateMask)
-{
-  return AsGecko()->HasStateDependentStyle(aElement, aStateMask);
-}
-
-nsRestyleHint
-StyleSetHandle::Ptr::HasStateDependentStyle(dom::Element* aElement,
-                                            CSSPseudoElementType aPseudoType,
-                                            dom::Element* aPseudoElement,
-                                            EventStates aStateMask)
-{
-  return AsGecko()->HasStateDependentStyle(aElement, aPseudoType, aPseudoElement, aStateMask);
-}
-
-void
-StyleSetHandle::Ptr::RootStyleContextAdded()
-{
-  AsGecko()->RootStyleContextAdded();
-}
-
-void
-StyleSetHandle::Ptr::RootStyleContextRemoved()
-{
-  RootStyleContextAdded();
-}
-
-} // namespace mozilla
-
-#endif // mozilla_StyleSetHandleInlines_h
diff --git a/layout/style/moz.build b/layout/style/moz.build
index 9452ff15ce..2f78f7772e 100644
--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -88,8 +88,6 @@ EXPORTS.mozilla += [
     'SheetType.h',
     'StyleAnimationValue.h',
     'StyleComplexColor.h',
-    'StyleSetHandle.h',
-    'StyleSetHandleInlines.h',
     'StyleSheet.h',
     'StyleSheetInfo.h',
     'StyleSheetInlines.h',
diff --git a/layout/style/nsAnimationManager.cpp b/layout/style/nsAnimationManager.cpp
index bfcf413ad6..f5f5eeed86 100644
--- a/layout/style/nsAnimationManager.cpp
+++ b/layout/style/nsAnimationManager.cpp
@@ -525,7 +525,7 @@ ResolvedStyleCache::Get(nsPresContext *aPresContext,
 
     nsCOMArray<nsIStyleRule> rules;
     rules.AppendObject(aKeyframeDeclaration);
-    RefPtr<nsStyleContext> resultStrong = aPresContext->StyleSet()->AsGecko()->
+    RefPtr<nsStyleContext> resultStrong = aPresContext->StyleSet()->
       ResolveStyleByAddingRules(aParentStyleContext, rules);
     mCache.Put(aKeyframeDeclaration, resultStrong);
     result = resultStrong;
@@ -1052,7 +1052,7 @@ CSSAnimationBuilder::GetComputedValue(nsPresContext* aPresContext,
   StyleAnimationValue computedValue;
 
   if (!mStyleWithoutAnimation) {
-    mStyleWithoutAnimation = aPresContext->StyleSet()->AsGecko()->
+    mStyleWithoutAnimation = aPresContext->StyleSet()->
       ResolveStyleWithoutAnimation(mTarget, mStyleContext,
                                    eRestyle_AllHintsWithAnimations);
   }
@@ -1098,7 +1098,7 @@ nsAnimationManager::BuildAnimations(nsStyleContext* aStyleContext,
     nsCSSKeyframesRule* rule =
       src.GetName().IsEmpty()
       ? nullptr
-      : mPresContext->StyleSet()->AsGecko()->KeyframesRuleForName(src.GetName());
+      : mPresContext->StyleSet()->KeyframesRuleForName(src.GetName());
     if (!rule) {
       continue;
     }
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index 006d8ffbba..68cbdbea2e 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -35,8 +35,7 @@
 #include "nsIDocument.h"
 
 #include "nsCSSPseudoElements.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "imgIRequest.h"
 #include "nsLayoutUtils.h"
 #include "nsCSSKeywords.h"
@@ -504,7 +503,7 @@ nsComputedDOMStyle::GetStyleContextForElementNoFlush(Element* aElement,
   if (!presContext)
     return nullptr;
 
-  StyleSetHandle styleSet = presShell->StyleSet();
+  nsStyleSet* styleSet = presShell->StyleSet();
 
   RefPtr<nsStyleContext> sc;
   if (aPseudo) {
@@ -543,7 +542,7 @@ nsComputedDOMStyle::GetStyleContextForElementNoFlush(Element* aElement,
       rules[i].swap(rules[length - i - 1]);
     }
 
-    sc = styleSet->AsGecko()->ResolveStyleForRules(parentContext, rules);
+    sc = styleSet->ResolveStyleForRules(parentContext, rules);
   }
 
   return sc.forget();
diff --git a/layout/style/nsDOMCSSAttrDeclaration.cpp b/layout/style/nsDOMCSSAttrDeclaration.cpp
index 7b68990333..ebdbb6641c 100644
--- a/layout/style/nsDOMCSSAttrDeclaration.cpp
+++ b/layout/style/nsDOMCSSAttrDeclaration.cpp
@@ -18,7 +18,8 @@
 #include "nsWrapperCacheInlines.h"
 #include "nsIFrame.h"
 #include "ActiveLayerTracker.h"
-#include "StyleSetHandle.h"
+
+class nsStyleSet;
 
 using namespace mozilla;
 using namespace mozilla::dom;
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index f2b914931f..1bba07ce6b 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -1659,7 +1659,7 @@ nsRuleNode::nsRuleNode(nsPresContext* aContext, nsRuleNode* aParent,
 
   NS_ASSERTION(IsRoot() || GetLevel() == aLevel, "not enough bits");
   NS_ASSERTION(IsRoot() || IsImportantRule() == aIsImportant, "yikes");
-  aContext->StyleSet()->AsGecko()->RuleNodeUnused(this, /* aMayGC = */ false);
+  aContext->StyleSet()->RuleNodeUnused(this, /* aMayGC = */ false);
 
   // nsStyleSet::GetContext depends on there being only one animation
   // rule.
@@ -3903,7 +3903,7 @@ nsRuleNode::SetFont(nsPresContext* aPresContext, nsStyleContext* aContext,
     if (variantAlternates & NS_FONT_VARIANT_ALTERNATES_FUNCTIONAL_MASK) {
       // fetch the feature lookup object from the styleset
       aFont->mFont.featureValueLookup =
-        aPresContext->StyleSet()->AsGecko()->GetFontFeatureValuesLookup();
+        aPresContext->StyleSet()->GetFontFeatureValuesLookup();
 
       NS_ASSERTION(variantAlternatesValue->GetPairValue().mYValue.GetUnit() ==
                    eCSSUnit_List, "function list not a list value");
diff --git a/layout/style/nsStyleContext.cpp b/layout/style/nsStyleContext.cpp
index da0853c7cc..3ffb04bdc2 100644
--- a/layout/style/nsStyleContext.cpp
+++ b/layout/style/nsStyleContext.cpp
@@ -31,8 +31,6 @@
 #include "RubyUtils.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ArenaObjectID.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 
 #include "mozilla/ReflowInput.h"
 #include "nsLayoutUtils.h"
@@ -160,7 +158,7 @@ nsStyleContext::~nsStyleContext()
 #endif
 
   nsPresContext *presContext = PresContext();
-  DebugOnly<nsStyleSet*> styleSet = presContext->PresShell()->StyleSet()->GetAsGecko();
+  DebugOnly<nsStyleSet*> styleSet = presContext->PresShell()->StyleSet();
   NS_ASSERTION(!styleSet ||
                styleSet->GetRuleTree() == mRuleNode->RuleTree() ||
                styleSet->IsInRuleTreeReconstruct(),
diff --git a/layout/style/nsStyleContext.h b/layout/style/nsStyleContext.h
index 18fcd3f47a..3cda29b90d 100644
--- a/layout/style/nsStyleContext.h
+++ b/layout/style/nsStyleContext.h
@@ -11,16 +11,13 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/RestyleLogging.h"
 #include "nsCSSAnonBoxes.h"
+#include "nsCSSPseudoElements.h"
 #include "nsStyleSet.h"
 #include "nsRuleNode.h"
 
 class nsIAtom;
 class nsPresContext;
 
-namespace mozilla {
-enum class CSSPseudoElementType : uint8_t;
-} // namespace mozilla
-
 /**
  * An nsStyleContext represents the computed style data for an element.
  * The computed style data are stored in a set of structs (see
diff --git a/layout/style/nsStyleSet.h b/layout/style/nsStyleSet.h
index 16ade5cc70..cdba2744ce 100644
--- a/layout/style/nsStyleSet.h
+++ b/layout/style/nsStyleSet.h
@@ -580,7 +580,7 @@ inline
 void nsRuleNode::AddRef()
 {
   if (mRefCnt++ == 0) {
-    mPresContext->StyleSet()->AsGecko()->RuleNodeInUse(this);
+    mPresContext->StyleSet()->RuleNodeInUse(this);
   }
 }
 
@@ -588,7 +588,7 @@ inline
 void nsRuleNode::Release()
 {
   if (--mRefCnt == 0) {
-    mPresContext->StyleSet()->AsGecko()->RuleNodeUnused(this, /* aMayGC = */ true);
+    mPresContext->StyleSet()->RuleNodeUnused(this, /* aMayGC = */ true);
   }
 }
 #endif
diff --git a/layout/style/nsTransitionManager.cpp b/layout/style/nsTransitionManager.cpp
index 00fdd2592d..8590501c79 100644
--- a/layout/style/nsTransitionManager.cpp
+++ b/layout/style/nsTransitionManager.cpp
@@ -530,7 +530,7 @@ nsTransitionManager::StyleContextChanged(dom::Element *aElement,
   // not stopping or starting right now.
   RefPtr<nsStyleContext> afterChangeStyle;
   if (collection) {
-    nsStyleSet* styleSet = mPresContext->StyleSet()->AsGecko();
+    nsStyleSet* styleSet = mPresContext->StyleSet();
     afterChangeStyle =
       styleSet->ResolveStyleWithoutAnimation(aElement, newStyleContext,
                                              eRestyle_CSSTransitions);
diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index cf4231c01f..24bb28b73a 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -38,8 +38,7 @@
 #include "nsFrameManager.h"
 #include "nsError.h"
 #include "nsCSSFrameConstructor.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "mozilla/gfx/Helpers.h"
 #include "nsDisplayList.h"
 #include "nsIScrollableFrame.h"
diff --git a/layout/xul/nsListBoxBodyFrame.cpp b/layout/xul/nsListBoxBodyFrame.cpp
index 0ff07bd912..4d57d0963d 100644
--- a/layout/xul/nsListBoxBodyFrame.cpp
+++ b/layout/xul/nsListBoxBodyFrame.cpp
@@ -26,8 +26,7 @@
 #include "nsStyleContext.h"
 #include "nsFontMetrics.h"
 #include "nsITimer.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsPIBoxObject.h"
 #include "nsLayoutUtils.h"
 #include "nsPIListBoxObject.h"
diff --git a/layout/xul/nsSplitterFrame.cpp b/layout/xul/nsSplitterFrame.cpp
index 468ccc6826..568bc83714 100644
--- a/layout/xul/nsSplitterFrame.cpp
+++ b/layout/xul/nsSplitterFrame.cpp
@@ -29,8 +29,7 @@
 #include "nsIServiceManager.h"
 #include "nsContainerFrame.h"
 #include "nsContentCID.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
+#include "nsStyleSet.h"
 #include "nsLayoutUtils.h"
 #include "nsDisplayList.h"
 #include "nsContentUtils.h"
diff --git a/layout/xul/tree/nsTreeStyleCache.cpp b/layout/xul/tree/nsTreeStyleCache.cpp
index a8802fe042..96aa489fee 100644
--- a/layout/xul/tree/nsTreeStyleCache.cpp
+++ b/layout/xul/tree/nsTreeStyleCache.cpp
@@ -6,8 +6,6 @@
 #include "nsTreeStyleCache.h"
 #include "nsStyleSet.h"
 #include "mozilla/dom/Element.h"
-#include "mozilla/StyleSetHandle.h"
-#include "mozilla/StyleSetHandleInlines.h"
 
 nsTreeStyleCache::Transition::Transition(DFAState aState, nsIAtom* aSymbol)
   : mState(aState), mInputSymbol(aSymbol)
@@ -78,7 +76,7 @@ nsTreeStyleCache::GetStyleContext(nsICSSPseudoComparator* aComparator,
   }
   if (!result) {
     // We missed the cache. Resolve this pseudo-style.
-    RefPtr<nsStyleContext> newResult = aPresContext->StyleSet()->AsGecko()->
+    RefPtr<nsStyleContext> newResult = aPresContext->StyleSet()->
       ResolveXULTreePseudoStyle(aContent->AsElement(), aPseudoElement,
                                 aContext, aComparator);
 
diff --git a/widget/gtk/nsMenu.cpp b/widget/gtk/nsMenu.cpp
index 073a4acf65..e0f5a5f5ba 100644
--- a/widget/gtk/nsMenu.cpp
+++ b/widget/gtk/nsMenu.cpp
@@ -9,7 +9,6 @@
 #include "mozilla/GuardObjects.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Move.h"
-#include "mozilla/StyleSetHandleInlines.h"
 #include "nsAutoPtr.h"
 #include "nsBindingManager.h"
 #include "nsComponentManagerUtils.h"
@@ -115,8 +114,7 @@ AttachXBLBindings(nsIContent* aContent) {
     }
 
     RefPtr<nsStyleContext> sc =
-        shell->StyleSet()->AsGecko()->ResolveStyleFor(aContent->AsElement(),
-                                                      nullptr);
+        shell->StyleSet()->ResolveStyleFor(aContent->AsElement(), nullptr);
     if (!sc) {
         return;
     }