Make PicturePile pile.

cc/picture.h

Index: cc/picture.h
diff --git a/cc/picture.h b/cc/picture.h
index bd8889ae3fdf21e73b1b8c23214d6b2d02565e72..563a5b7f50964dcdc758ac328428e7f281546acd 100644
--- a/cc/picture.h
+++ b/cc/picture.h
@@ -19,24 +19,27 @@ struct RenderingStats;
 class CC_EXPORT Picture
     : public base::RefCountedThreadSafe<Picture> {
 public:
-  static scoped_refptr<Picture> Create();
+  static scoped_refptr<Picture> Create(gfx::Rect layer_rect);
 
   const gfx::Rect& LayerRect() const { return layer_rect_; }
   const gfx::Rect& OpaqueRect() const { return opaque_rect_; }
 
   // Make a thread-safe clone for rasterizing with.
-  scoped_refptr<Picture> Clone();
+  scoped_refptr<Picture> Clone() const;
 
   // Record a paint operation. To be able to safely use this SkPicture for
   // playback on a different thread this can only be called once.
-  void Record(ContentLayerClient*, gfx::Rect layer_rect, RenderingStats&);
+  void Record(ContentLayerClient*, RenderingStats&);
+
+  // Has Record() been called yet?
+  bool HasRecording() const { return picture_.get(); }
 
   // Raster this Picture's layer_rect into the given canvas.
   // Assumes contentsScale have already been applied.
   void Raster(SkCanvas* canvas);
 
 private:
-  Picture();
+  Picture(gfx::Rect layer_rect);
   // This constructor assumes SkPicture is already ref'd and transfers
   // ownership to this picture.
   Picture(SkPicture*, gfx::Rect layer_rect, gfx::Rect opaque_rect);