Changes subtreeShouldRenderToSeparateSurface logic to account for explicit clipping

cc/layer_impl.h

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_LAYER_IMPL_H_
 #define CC_LAYER_IMPL_H_
 
 #include <public/WebFilterOperations.h>
 #include <string>
 
@@ skipping 263 matching lines @@
     void setHorizontalScrollbarLayer(ScrollbarLayerImpl*);
     ScrollbarLayerImpl* horizontalScrollbarLayer();
     const ScrollbarLayerImpl* horizontalScrollbarLayer() const;
 
     void setVerticalScrollbarLayer(ScrollbarLayerImpl*);
     ScrollbarLayerImpl* verticalScrollbarLayer();
     const ScrollbarLayerImpl* verticalScrollbarLayer() const;
 
     gfx::Rect layerRectToContentRect(const gfx::RectF& layerRect) const;
 
+    virtual bool canClipSelf() const { return false; }
+
 protected:
     LayerImpl(LayerTreeImpl* layerImpl, int);
 
     // Get the color and size of the layer's debug border.
     virtual void getDebugBorderProperties(SkColor*, float* width) const;
 
     void appendDebugBorderQuad(QuadSink&, const SharedQuadState*, AppendQuadsData&) const;
 
     virtual void dumpLayerProperties(std::string*, int indent) const;
     static std::string indentString(int indent);
@@ skipping 104 matching lines @@
     // Group of properties that need to be computed based on the layer tree
     // hierarchy before layers can be drawn.
     DrawProperties<LayerImpl, RenderSurfaceImpl> m_drawProperties;
 
     DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }
 
 #endif  // CC_LAYER_IMPL_H_