cc: Measure compositor timing with finer granularity

cc/trees/layer_tree_host_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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 101 matching lines @@
       scoped_ptr<AnimationEventsVector> events) = 0;
   // Returns true if resources were deleted by this call.
   virtual bool ReduceContentsTextureMemoryOnImplThread(
       size_t limit_bytes,
       int priority_cutoff) = 0;
   virtual bool IsInsideDraw() = 0;
   virtual void RenewTreePriority() = 0;
   virtual void PostDelayedAnimationTaskOnImplThread(const base::Closure& task,
                                                     base::TimeDelta delay) = 0;
   virtual void DidActivateSyncTree() = 0;
+  virtual void WillPrepareTiles() = 0;
   virtual void DidPrepareTiles() = 0;
 
   // Called when page scale animation has completed on the impl thread.
   virtual void DidCompletePageScaleAnimationOnImplThread() = 0;
 
   // Called when output surface asks for a draw.
   virtual void OnDrawForOutputSurface() = 0;
 
   virtual void PostFrameTimingEventsOnImplThread(
       scoped_ptr<FrameTimingTracker::CompositeTimingSet> composite_events,
@@ skipping 642 matching lines @@
   scoped_ptr<FrameTimingTracker> frame_timing_tracker_;
 
   scoped_ptr<Viewport> viewport_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_