Align Element.ScrollIntoView() with the spec.

This also removes the (unused) shadow alias from nsIDOMHTMLElement
which used the different calling convention.

This resolves #927

dom/base/Element.cpp

@@ -687,19 +687,23 @@ Element::GetScrollFrame(nsIFrame **aStyledFrame, bool aFlushLayout)
 }
 
 void
-Element::ScrollIntoView()
+Element::ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject)
 {
-  ScrollIntoView(ScrollIntoViewOptions());
+  if (aObject.IsScrollIntoViewOptions()) {
-}
+    return ScrollIntoView(aObject.GetAsScrollIntoViewOptions());
-
-void
-Element::ScrollIntoView(bool aTop)
-{
-  ScrollIntoViewOptions options;
-  if (!aTop) {
-    options.mBlock = ScrollLogicalPosition::End;
   }
-  ScrollIntoView(options);
+
+  MOZ_DIAGNOSTIC_ASSERT(aObject.IsBoolean());
+
+  ScrollIntoViewOptions options;
+  if (aObject.GetAsBoolean()) {
+    options.mBlock = ScrollLogicalPosition::Start;
+    options.mInline = ScrollLogicalPosition::Nearest;
+  } else {
+    options.mBlock = ScrollLogicalPosition::End;
+    options.mInline = ScrollLogicalPosition::Nearest;
+  }
+  return ScrollIntoView(options);
 }
 
 void
@@ -716,9 +720,41 @@ Element::ScrollIntoView(const ScrollIntoViewOptions &aOptions)
     return;
   }
 
-  int16_t vpercent = (aOptions.mBlock == ScrollLogicalPosition::Start)
+  int16_t vpercent = nsIPresShell::SCROLL_CENTER;
-                       ? nsIPresShell::SCROLL_TOP
+  switch (aOptions.mBlock) {
-                       : nsIPresShell::SCROLL_BOTTOM;
+    case ScrollLogicalPosition::Start:
+      vpercent = nsIPresShell::SCROLL_TOP;
+      break;
+    case ScrollLogicalPosition::Center:
+      vpercent = nsIPresShell::SCROLL_CENTER;
+      break;
+    case ScrollLogicalPosition::End:
+      vpercent = nsIPresShell::SCROLL_BOTTOM;
+      break;
+    case ScrollLogicalPosition::Nearest:
+      vpercent = nsIPresShell::SCROLL_MINIMUM;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected ScrollLogicalPosition value");
+  }
+
+  int16_t hpercent = nsIPresShell::SCROLL_CENTER;
+  switch (aOptions.mInline) {
+    case ScrollLogicalPosition::Start:
+      hpercent = nsIPresShell::SCROLL_LEFT;
+      break;
+    case ScrollLogicalPosition::Center:
+      hpercent = nsIPresShell::SCROLL_CENTER;
+      break;
+    case ScrollLogicalPosition::End:
+      hpercent = nsIPresShell::SCROLL_RIGHT;
+      break;
+    case ScrollLogicalPosition::Nearest:
+      hpercent = nsIPresShell::SCROLL_MINIMUM;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected ScrollLogicalPosition value");
+  }
 
   uint32_t flags = nsIPresShell::SCROLL_OVERFLOW_HIDDEN;
   if (aOptions.mBehavior == ScrollBehavior::Smooth) {
@@ -731,7 +767,9 @@ Element::ScrollIntoView(const ScrollIntoViewOptions &aOptions)
                                    nsIPresShell::ScrollAxis(
                                      vpercent,
                                      nsIPresShell::SCROLL_ALWAYS),
-                                   nsIPresShell::ScrollAxis(),
+                                   nsIPresShell::ScrollAxis(
+                                     hpercent,
+                                     nsIPresShell::SCROLL_ALWAYS),
                                    flags);
 }
 

dom/base/Element.h

@@ -818,9 +818,10 @@ public:
     return slots ? slots->mShadowRoot.get() : nullptr;
   }
 
-  void ScrollIntoView();
+private:
-  void ScrollIntoView(bool aTop);
   void ScrollIntoView(const ScrollIntoViewOptions &aOptions);
+public:
+  void ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject);
   void Scroll(double aXScroll, double aYScroll);
   void Scroll(const ScrollToOptions& aOptions);
   void ScrollTo(double aXScroll, double aYScroll);

dom/html/nsGenericHTMLElement.h

@@ -396,13 +396,6 @@ public:
   }
   NS_IMETHOD InsertAdjacentHTML(const nsAString& position,
                                 const nsAString& text) final override;
-  NS_IMETHOD ScrollIntoView(bool top, uint8_t _argc) final override {
-    if (!_argc) {
-      top = true;
-    }
-    mozilla::dom::Element::ScrollIntoView(top);
-    return NS_OK;
-  }
   NS_IMETHOD GetOffsetParent(nsIDOMElement** aOffsetParent)
     final override {
     mozilla::dom::Element* offsetParent = GetOffsetParent();

dom/interfaces/html/nsIDOMHTMLElement.idl

@@ -58,7 +58,6 @@ interface nsIDOMHTMLElement : nsIDOMElement
 
 
   // CSSOM View
-  [optional_argc] void scrollIntoView([optional] in boolean top);
   readonly attribute nsIDOMElement    offsetParent;
   readonly attribute long             offsetTop;
   readonly attribute long             offsetLeft;

dom/webidl/Element.webidl

@@ -164,9 +164,10 @@ interface Element : Node {
 };
 
 // http://dev.w3.org/csswg/cssom-view/
-enum ScrollLogicalPosition { "start", "end" };
+enum ScrollLogicalPosition { "start", "center", "end", "nearest" };
 dictionary ScrollIntoViewOptions : ScrollOptions {
   ScrollLogicalPosition block = "start";
+  ScrollLogicalPosition inline = "nearest";
 };
 
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-element-interface
@@ -175,8 +176,7 @@ partial interface Element {
   DOMRect getBoundingClientRect();
 
   // scrolling
-  void scrollIntoView(boolean top);
+  void scrollIntoView(optional (boolean or ScrollIntoViewOptions) arg);
-  void scrollIntoView(optional ScrollIntoViewOptions options);
   // None of the CSSOM attributes are [Pure], because they flush
            attribute long scrollTop;   // scroll on setting
            attribute long scrollLeft;  // scroll on setting