cc: Add a blocksPendingCommit flag to LayerImpl

cc/layer.h

 // Copyright 2010 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_H_
 #define CC_LAYER_H_
 
 #include <public/WebFilterOperations.h>
 #include <string>
 #include <vector>
@@ skipping 259 matching lines @@
 
     virtual void notifyAnimationStarted(const AnimationEvent&, double wallClockTime);
     virtual void notifyAnimationFinished(double wallClockTime);
 
     virtual Region visibleContentOpaqueRegion() const;
 
     virtual ScrollbarLayer* toScrollbarLayer();
 
     gfx::Rect layerRectToContentRect(const gfx::RectF& layerRect) const;
 
+    // In impl-side painting, this returns true if this layer type is not
+    // compatible with the main thread running freely, such as a double-buffered
+    // canvas that doesn't want to be triple-buffered across all three trees.
+    virtual bool blocksPendingCommit() const;
+
 protected:
     friend class LayerImpl;
     friend class TreeSynchronizer;
     virtual ~Layer();
 
     Layer();
 
     void setNeedsCommit();
     void setNeedsFullTreeSync();
 
@@ skipping 88 matching lines @@
     WebKit::WebLayerScrollClient* m_layerScrollClient;
 
     DrawProperties<Layer, RenderSurface> m_drawProperties;
 };
 
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*);
 
 }  // namespace cc
 
 #endif  // CC_LAYER_H_