Add support for calculating the position of the top controls in the cc layer.

cc/compositor_frame_metadata.h

Index: cc/compositor_frame_metadata.h
diff --git a/cc/compositor_frame_metadata.h b/cc/compositor_frame_metadata.h
index 92a48ffba2c4aaff0a7955bd41ddf99e20e44b1c..b7111622519086b52cdcd27438638a83e8787824 100644
--- a/cc/compositor_frame_metadata.h
+++ b/cc/compositor_frame_metadata.h
@@ -32,6 +32,7 @@ class CC_EXPORT CompositorFrameMetadata
   // Used to position the Android location top bar, whose precise
   // position is computed by the renderer compositor.
   gfx::Vector2dF location_bar_offset;
+  gfx::Vector2dF content_offset;
 };
 
 }  // namespace cc