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

cc/layer_tree_host_impl.h

Index: cc/layer_tree_host_impl.h
diff --git a/cc/layer_tree_host_impl.h b/cc/layer_tree_host_impl.h
index f6a4c65003b6d5d4060356d4f4b9f703c0f588b2..8748b70349493bb19ebb373b62c7aa6d2f6286a0 100644
--- a/cc/layer_tree_host_impl.h
+++ b/cc/layer_tree_host_impl.h
@@ -28,6 +28,7 @@ class LayerTreeHostImplTimeSourceAdapter;
 class PageScaleAnimation;
 class RenderPassDrawQuad;
 class ResourceProvider;
+class RenderingStatsSubscriber;
 struct RendererCapabilities;
 struct RenderingStats;
 
@@ -224,6 +225,8 @@ public:
     void setNeedsRedraw();
 
     void renderingStats(RenderingStats*) const;
+    void startRecordingRenderingStats();
+    void stopRecordingRenderingStats(RenderingStats*);
 
     void updateRootScrollLayerImplTransform();
 
@@ -345,6 +348,7 @@ private:
 
     scoped_ptr<FrameRateCounter> m_fpsCounter;
     scoped_ptr<DebugRectHistory> m_debugRectHistory;
+    scoped_ptr<RenderingStatsSubscriber> m_renderingStatsSubscriber;
 
     size_t m_numImplThreadScrolls;
     size_t m_numMainThreadScrolls;