cc: add PaintTimeCounter to keep track of per frame paint time

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 d1019c158cc0747eb9f39e6bd231183bda94ad76..eeb8c871ca22b7b240b011bf6cfdb3715b8ed971 100644
--- a/cc/layer_tree_host_impl.h
+++ b/cc/layer_tree_host_impl.h
@@ -33,6 +33,7 @@ class LayerImpl;
 class LayerTreeHostImplTimeSourceAdapter;
 class LayerTreeImpl;
 class PageScaleAnimation;
+class PaintTimeCounter;
 class RenderPassDrawQuad;
 class ResourceProvider;
 struct RendererCapabilities;
@@ -200,6 +201,7 @@ public:
        size_t memoryUseBytes);
 
     FrameRateCounter* fpsCounter() const { return m_fpsCounter.get(); }
+    PaintTimeCounter* paintTimeCounter() const { return m_paintTimeCounter.get(); }
     DebugRectHistory* debugRectHistory() const { return m_debugRectHistory.get(); }
     ResourceProvider* resourceProvider() const { return m_resourceProvider.get(); }
 
@@ -210,6 +212,8 @@ public:
     void setDebugState(const LayerTreeDebugState& debugState) { m_debugState = debugState; }
     const LayerTreeDebugState& debugState() const { return m_debugState; }
 
+    void savePaintTime(double totalPaintTimeInSeconds);
+
     class CC_EXPORT CullRenderPassesWithCachedTextures {
     public:
         bool shouldRemoveRenderPass(const RenderPassDrawQuad&, const FrameData&) const;
@@ -326,6 +330,7 @@ private:
     PinchZoomViewport m_pinchZoomViewport;
 
     scoped_ptr<FrameRateCounter> m_fpsCounter;
+    scoped_ptr<PaintTimeCounter> m_paintTimeCounter;
     scoped_ptr<DebugRectHistory> m_debugRectHistory;
 
     int64 m_numImplThreadScrolls;