GPU benchmarks should track the frequency of impl-thread vs. main-thread scrolls

cc/CCRenderingStats.h

 // Copyright 2012 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 CCRenderingStats_h
 #define CCRenderingStats_h
 
 namespace cc {
 
 struct CCRenderingStats {
     // FIXME: Rename these to animationFrameCount and screenFrameCount, crbug.com/138641.
     int numAnimationFrames;
     int numFramesSentToScreen;
     int droppedFrameCount;
     double totalPaintTimeInSeconds;
     double totalRasterizeTimeInSeconds;
     double totalCommitTimeInSeconds;
     size_t totalCommitCount;
+    size_t numImplThreadScrolls;
+    size_t numMainThreadScrolls;
 
     CCRenderingStats()
         : numAnimationFrames(0)
         , numFramesSentToScreen(0)
         , droppedFrameCount(0)
         , totalPaintTimeInSeconds(0)
         , totalRasterizeTimeInSeconds(0)
         , totalCommitTimeInSeconds(0)
         , totalCommitCount(0)
+        , numImplThreadScrolls(0)
+        , numMainThreadScrolls(0)
     {
     }
 };
 
 }
 
 #endif