Track the cost of impl-side painting.

cc/picture_pile_impl.h

Index: cc/picture_pile_impl.h
===================================================================
--- cc/picture_pile_impl.h	(revision 170195)
+++ cc/picture_pile_impl.h	(working copy)
@@ -14,6 +14,7 @@
 
 namespace cc {
 class PicturePile;
+struct RenderingStats;
 
 class CC_EXPORT PicturePileImpl : public base::RefCounted<PicturePileImpl> {
 public:
@@ -25,7 +26,7 @@
   // Raster a subrect of this PicturePileImpl into the given canvas.
   // It's only safe to call paint on a cloned version.
   // It is assumed that contentsScale has already been applied to this canvas.
-  void Raster(SkCanvas* canvas, gfx::Rect rect);
+  void Raster(SkCanvas* canvas, gfx::Rect rect, RenderingStats* stats);
 
 private:
   friend class PicturePile;