Fix border radius on composited children.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
index c83206a1dda69d6eea48bdde6783e8da572f2744..c8cf7e0657ae94e07510b34769535db9ee0e4461 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
@@ -375,6 +375,9 @@ class CORE_EXPORT CompositedLayerMapping final : public GraphicsLayerClient {
   void updateInternalHierarchy();
   void updatePaintingPhases();
   bool updateClippingLayers(bool needsAncestorClip, bool needsDescendantClip);
+  bool updateClippingLayers(bool needsAncestorClip,
+                            bool needsAncestorClippingMask,
+                            bool needsDescendantClip);
   bool updateChildTransformLayer(bool needsChildTransformLayer);
   bool updateOverflowControlsLayers(bool needsHorizontalScrollbarLayer,
                                     bool needsVerticalScrollbarLayer,
@@ -468,10 +471,16 @@ class CORE_EXPORT CompositedLayerMapping final : public GraphicsLayerClient {
       const GraphicsLayerPaintInfo&,
       const Vector<GraphicsLayerPaintInfo>& layers);
 
-  // Return true if |m_owningLayer|'s compositing ancestor is not a descendant
-  // (inclusive) of the clipping container for |m_owningLayer|.
-  bool owningLayerClippedByLayerNotAboveCompositedAncestor(
-      const PaintLayer* scrollParent);
+  // Return true in |owningLayerIsClipped| iff |m_owningLayer|'s compositing
+  // ancestor is not a descendant (inclusive) of the clipping container for
+  // |m_owningLayer|. Return true in |owningLayerIsMasked| iff
+  // |owningLayerIsClipped| is true and |m_owningLayer|'s compositing ancestor
+  // is not a descendant (inclusive) of a container that applies a mask for
+  // |m_owningLayer|.
+  void owningLayerClippedOrMaskedByLayerNotAboveCompositedAncestor(
+      const PaintLayer* scrollParent,
+      bool& owningLayerIsClipped,
+      bool& owningLayerIsMasked);

[Stephen Chennney, 2016/11/08 21:42:51]

Not sure if it's a good idea to set two things with the same method, but it
avoids computing all the clipping container info twice.

 
   const PaintLayer* scrollParent();
 
@@ -522,6 +531,11 @@ class CORE_EXPORT CompositedLayerMapping final : public GraphicsLayerClient {
 
   // Only used if we are clipped by an ancestor which is not a stacking context.
   std::unique_ptr<GraphicsLayer> m_ancestorClippingLayer;
+
+  // Only used is there is an m_ancestorClippingLayer that also needs to apply
+  // a clipping mask (for CSS clips or border radius).
+  std::unique_ptr<GraphicsLayer> m_ancestorClippingMaskLayer;
+
   std::unique_ptr<GraphicsLayer> m_graphicsLayer;
 
   // Only used if we have clipping on a stacking context with compositing