NOT READY FOR REVIEW - switch to a subscriber model for rendering stats

cc/rendering_stats.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 RenderingStats {
     // FIXME: Rename these to animationFrameCount and screenFrameCount, crbug.com/138641.
     int numAnimationFrames;
     int numFramesSentToScreen;
     int droppedFrameCount;
+    double frameRateAverage;
+    double frameRateStandardDeviation;
     double totalPaintTimeInSeconds;
     double totalRasterizeTimeInSeconds;
     double totalCommitTimeInSeconds;
     size_t totalCommitCount;
     size_t numImplThreadScrolls;
     size_t numMainThreadScrolls;
 
-    RenderingStats()
-        : numAnimationFrames(0)
-        , numFramesSentToScreen(0)
-        , droppedFrameCount(0)
-        , totalPaintTimeInSeconds(0)
-        , totalRasterizeTimeInSeconds(0)
-        , totalCommitTimeInSeconds(0)
-        , totalCommitCount(0)
-        , numImplThreadScrolls(0)
-        , numMainThreadScrolls(0)
-    {
-    }
+    RenderingStats();
 };
 
-}
+}  // namespace cc
 
 #endif