diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index c683a19605..54f965e9d2 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -855,8 +855,6 @@ nsCSSRendering::PaintOutline(nsPresContext* aPresContext,
                              const nsRect& aBorderArea,
                              nsStyleContext* aStyleContext)
 {
-  nscoord             twipsRadii[8];
-
   // Get our style context's color struct.
   const nsStyleOutline* ourOutline = aStyleContext->StyleOutline();
   MOZ_ASSERT(ourOutline != NS_STYLE_BORDER_STYLE_NONE,
@@ -898,24 +896,6 @@ nsCSSRendering::PaintOutline(nsPresContext* aPresContext,
   if (innerRect.Contains(aDirtyRect))
     return;
 
-  nsRect outerRect = innerRect;
-  outerRect.Inflate(width, width);
-
-  // get the radius for our outline
-  nsIFrame::ComputeBorderRadii(ourOutline->mOutlineRadius, aBorderArea.Size(),
-                               outerRect.Size(), Sides(), twipsRadii);
-
-  // Get our conversion values
-  nscoord twipsPerPixel = aPresContext->DevPixelsToAppUnits(1);
-
-  // get the outer rectangles
-  Rect oRect(NSRectToRect(outerRect, twipsPerPixel));
-
-  // convert the radii
-  nsMargin outlineMargin(width, width, width, width);
-  RectCornerRadii outlineRadii;
-  ComputePixelRadii(twipsRadii, twipsPerPixel, &outlineRadii);
-
   if (outlineStyle == NS_STYLE_BORDER_STYLE_AUTO) {
     if (nsLayoutUtils::IsOutlineStyleAutoEnabled()) {
       nsITheme* theme = aPresContext->GetTheme();
@@ -935,6 +915,36 @@ nsCSSRendering::PaintOutline(nsPresContext* aPresContext,
     outlineStyle = NS_STYLE_BORDER_STYLE_SOLID;
   }
 
+  RectCornerRadii outlineRadii;
+  nsRect outerRect = innerRect;
+  outerRect.Inflate(width, width);
+
+  const nscoord oneDevPixel = aPresContext->AppUnitsPerDevPixel();
+  Rect oRect(NSRectToRect(outerRect, oneDevPixel));
+
+  const Float outlineWidths[4] = {
+      Float(width) / oneDevPixel, Float(width) / oneDevPixel,
+      Float(width) / oneDevPixel, Float(width) / oneDevPixel};
+
+  // convert the radii
+  nscoord twipsRadii[8];
+
+  // get the radius for our outline
+  if (nsLayoutUtils::HasNonZeroCorner(ourOutline->mOutlineRadius)) {
+    nsIFrame::ComputeBorderRadii(ourOutline->mOutlineRadius, aBorderArea.Size(),
+                                 outerRect.Size(), Sides(), twipsRadii);
+    ComputePixelRadii(twipsRadii, oneDevPixel, &outlineRadii);
+  } else if (aForFrame->GetBorderRadii(twipsRadii)) {
+    RectCornerRadii innerRadii;
+    ComputePixelRadii(twipsRadii, oneDevPixel, &innerRadii);
+
+    Float devPixelOffset = aPresContext->AppUnitsToFloatDevPixels(offset);
+    const Float widths[4] = {
+        outlineWidths[0] + devPixelOffset, outlineWidths[1] + devPixelOffset,
+        outlineWidths[2] + devPixelOffset, outlineWidths[3] + devPixelOffset};
+    nsCSSBorderRenderer::ComputeOuterRadii(innerRadii, widths, &outlineRadii);
+  }
+
   uint8_t outlineStyles[4] = { outlineStyle, outlineStyle,
                                outlineStyle, outlineStyle };
 
@@ -947,12 +957,7 @@ nsCSSRendering::PaintOutline(nsPresContext* aPresContext,
                                outlineColor,
                                outlineColor };
 
-  // convert the border widths
-  Float outlineWidths[4] = { Float(width / twipsPerPixel),
-                             Float(width / twipsPerPixel),
-                             Float(width / twipsPerPixel),
-                             Float(width / twipsPerPixel) };
-  Rect dirtyRect = NSRectToRect(aDirtyRect, twipsPerPixel);
+  Rect dirtyRect = NSRectToRect(aDirtyRect, oneDevPixel);
 
   nsIDocument* document = nullptr;
   nsIContent* content = aForFrame->GetContent();
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index fa28ea5f87..825c564211 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -3757,18 +3757,23 @@ nsDisplayOutline::Paint(nsDisplayListBuilder* aBuilder,
                                mFrame->StyleContext());
 }
 
+bool nsDisplayOutline::HasRadius() const {
+  if (nsLayoutUtils::HasNonZeroCorner(mFrame->StyleOutline()->mOutlineRadius)) {
+    return true;
+  }
+  return nsLayoutUtils::HasNonZeroCorner(mFrame->StyleBorder()->mBorderRadius);
+}
+
 bool
 nsDisplayOutline::IsInvisibleInRect(const nsRect& aRect)
 {
   const nsStyleOutline* outline = mFrame->StyleOutline();
   nsRect borderBox(ToReferenceFrame(), mFrame->GetSize());
-  if (borderBox.Contains(aRect) &&
-      !nsLayoutUtils::HasNonZeroCorner(outline->mOutlineRadius)) {
-    if (outline->mOutlineOffset >= 0) {
-      // aRect is entirely inside the border-rect, and the outline isn't
-      // rendered inside the border-rect, so the outline is not visible.
-      return true;
-    }
+  if (borderBox.Contains(aRect) && !HasRadius() &&
+    outline->mOutlineOffset >= 0) {
+    // aRect is entirely inside the border-rect, and the outline isn't
+    // rendered inside the border-rect, so the outline is not visible.
+    return true;
   }
 
   return false;
diff --git a/layout/base/nsDisplayList.h b/layout/base/nsDisplayList.h
index 2b4efd86ef..2f3f53b7fc 100644
--- a/layout/base/nsDisplayList.h
+++ b/layout/base/nsDisplayList.h
@@ -3220,6 +3220,9 @@ public:
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) override;
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx) override;
   NS_DISPLAY_DECL_NAME("Outline", TYPE_OUTLINE)
+
+private:
+  bool HasRadius() const;
 };
 
 /**
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 4f95ddaeb0..9de0f13c00 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -510,6 +510,8 @@ nsStyleBorder::CalcDifference(const nsStyleBorder& aNewData) const
     }
   }
 
+  // Note that border radius is used as a fallback for outline radius, if set.
+  // Any optimizations here should apply to both.
   if (mBorderRadius != aNewData.mBorderRadius ||
       !mBorderColors != !aNewData.mBorderColors) {
     return nsChangeHint_RepaintFrame;