Add flag for drawing layers to screen with Ganesh

cc/resources/picture_pile_impl.h

Index: cc/resources/picture_pile_impl.h
diff --git a/cc/resources/picture_pile_impl.h b/cc/resources/picture_pile_impl.h
index f3bc98cbc479cbb155ec2dbf48ead9cd0783206d..e058c46c4b4a640a7c4bfca11a900d730270ae9d 100644
--- a/cc/resources/picture_pile_impl.h
+++ b/cc/resources/picture_pile_impl.h
@@ -53,6 +53,15 @@ class CC_EXPORT PicturePileImpl : public PicturePileBase {
       float contents_scale,
       RasterStats* raster_stats);
 
+  // Similar to the above Raster method, but this is a convenience method
+  // for when it is known that the raster is going to an intermediate bitmap
+  // that itself will then be blended and thus that a canvas clear is required.
+  void RasterToBitmap(
+      SkCanvas* canvas,
+      gfx::Rect canvas_rect,
+      float contents_scale,
+      RasterStats* raster_stats);
+
   skia::RefPtr<SkPicture> GetFlattenedPicture();
 
   struct CC_EXPORT Analysis {