Throttle prepaints to avoid colliding with post-load work

cc/layer_tree_host.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 CCLayerTreeHost_h
 #define CCLayerTreeHost_h
 
 #include <limits>
 
 #include "IntRect.h"
 #include "base/basictypes.h"
+#include "base/cancelable_callback.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/animation_events.h"
 #include "cc/graphics_context.h"
 #include "cc/layer_tree_host_client.h"
 #include "cc/layer_tree_host_common.h"
 #include "cc/occlusion_tracker.h"
 #include "cc/prioritized_texture_manager.h"
 #include "cc/proxy.h"
@@ skipping 189 matching lines @@
 private:
     typedef std::vector<scoped_refptr<Layer> > LayerList;
 
     void initializeRenderer();
 
     void update(Layer*, TextureUpdateQueue&, const OcclusionTracker*);
     bool paintLayerContents(const LayerList&, TextureUpdateQueue&);
     bool paintMasksForRenderSurface(Layer*, TextureUpdateQueue&);
 
     void updateLayers(Layer*, TextureUpdateQueue&);
+    void triggerPrepaint();
 
     void prioritizeTextures(const LayerList&, OverdrawMetrics&); 
     void setPrioritiesForSurfaces(size_t surfaceMemoryBytes);
     void setPrioritiesForLayers(const LayerList&);
     size_t calculateMemoryForRenderSurfaces(const LayerList& updateList);
 
     void animateLayers(double monotonicTime);
     bool animateLayersRecursive(Layer* current, double monotonicTime);
     void setAnimationEventsRecursive(const AnimationEventsVector&, Layer*, double wallClockTime);
 
     bool m_animating;
     bool m_needsAnimateLayers;
 
+    base::CancelableClosure m_prepaintCallback;
+
     LayerTreeHostClient* m_client;
 
     int m_commitNumber;
     RenderingStats m_renderingStats;
 
     scoped_ptr<Proxy> m_proxy;
     bool m_rendererInitialized;
     bool m_contextLost;
     int m_numTimesRecreateShouldFail;
     int m_numFailedRecreateAttempts;
@@ skipping 29 matching lines @@
     size_t m_partialTextureUpdateRequests;
 
     static bool s_needsFilterContext;
 
     DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif