cc: Enable composited border-radius scrolling.

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

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 572 matching lines @@
   const PaintLayer* compositing_ancestor =
       owning_layer_.EnclosingLayerWithCompositedLayerMapping(kExcludeSelf);
   if (!compositing_ancestor)
     return;
 
   const LayoutBoxModelObject* clipping_container =
       owning_layer_.ClippingContainer();
   if (!clipping_container)
     return;
 
-  if (clipping_container->EnclosingLayer() == scroll_parent)
-    return;
-
   if (compositing_ancestor->GetLayoutObject().IsDescendantOf(
           clipping_container))
     return;
 
   // We ignore overflow clip here; we want composited overflow content to
   // behave as if it lives in an unclipped universe so it can prepaint, etc.
   // This means that we need to check if we are actually clipped before
   // setting up m_ancestorClippingLayer otherwise
   // updateAncestorClippingLayerGeometry will fail as the clip rect will be
   // infinite.
@@ skipping 10 matching lines @@
   owning_layer_is_clipped = parent_clip_rect != LayoutRect::InfiniteIntRect();
 
   // TODO(schenney): CSS clips are not applied to composited children, and
   // should be via mask or by compositing the parent too.
   // https://bugs.chromium.org/p/chromium/issues/detail?id=615870
   DCHECK(clipping_container->Style());
   owning_layer_is_masked =
       owning_layer_is_clipped &&
       clipping_container->Style()->HasBorderRadius() &&
       !AncestorRoundedCornersWontClip(GetLayoutObject(), *clipping_container);
+
+  if (clipping_container->EnclosingLayer() == scroll_parent)
+    owning_layer_is_clipped = owning_layer_is_masked;
 }
 
 const PaintLayer* CompositedLayerMapping::ScrollParent() {
   const PaintLayer* scroll_parent = owning_layer_.ScrollParent();
   if (scroll_parent && !scroll_parent->NeedsCompositedScrolling())
     return nullptr;
   return scroll_parent;
 }
 
 bool CompositedLayerMapping::UpdateGraphicsLayerConfiguration() {
@@ skipping 2998 matching lines @@
   } else if (graphics_layer == decoration_outline_layer_.get()) {
     name = "Decoration Layer";
   } else {
     NOTREACHED();
   }
 
   return name;
 }
 
 }  // namespace blink