cc: Partial tile update for one-copy raster.

cc/resources/raster_source.h

Index: cc/resources/raster_source.h
diff --git a/cc/resources/raster_source.h b/cc/resources/raster_source.h
index 171d2a55412b9da90f95b53c4cac59383ed21f17..ac0eae5f22f4326eda00a599a7be7a675c1ea32e 100644
--- a/cc/resources/raster_source.h
+++ b/cc/resources/raster_source.h
@@ -42,7 +42,8 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
   // this raster source via this call.
   virtual void PlaybackToCanvas(SkCanvas* canvas,
                                 const gfx::Rect& canvas_rect,
-                                float contents_scale) const = 0;
+                                float contents_scale,
+                                bool partial_update) const = 0;
 
   // Similar to above, except that the canvas passed here can (or was already)
   // rasterized into by another raster source. That is, it is not safe to clear