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 6ee087cb6ff8003890f1d4aad870f15329138644..3e98bdec89d089ec420f32847ca17490298ca68b 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
@@ -117,6 +117,10 @@ class CORE_EXPORT CompositedLayerMapping final : public GraphicsLayerClient {
     return m_ancestorClippingLayer.get();
   }
 
+  GraphicsLayer* ancestorClippingMaskLayer() const {
+    return m_ancestorClippingMaskLayer.get();
+  }
+
   GraphicsLayer* foregroundLayer() const { return m_foregroundLayer.get(); }
 
   GraphicsLayer* backgroundLayer() const { return m_backgroundLayer.get(); }
@@ -383,6 +387,9 @@ 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,
@@ -477,10 +484,16 @@ 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);
 
   const PaintLayer* scrollParent();
 
@@ -529,9 +542,20 @@ class CORE_EXPORT CompositedLayerMapping final : public GraphicsLayerClient {
   // In this case B is clipped by another layer that doesn't happen to be its
   // ancestor: A.  So we create an ancestor clipping layer for B, [+], which
   // ensures that B is clipped as if it had been A's descendant.
+  // In addition, the m_ancestorClippingLayer will have an associated
+  // mask layer if the ancestor, A, has a border radius that requires a
+  // rounded corner clip rect. The mask is not part of the layer tree; rather
+  // it is attached to the m_ancestorClippingLayer itself.
+  //
+  // Layers that require a CSS mask also have a mask layer attached to them.
 
   // 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