Plumb physical backing size from RWHV to renderer CC.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 62e50c935b9d9e0bc0e9f59fc07a8ee35fa7551b..3c5cd92fa3dc8e58cb4a4ad1f5c225b0be5e0d3a 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -797,8 +797,9 @@ IPC_MESSAGE_ROUTED0(ViewMsg_Close)
 // the view's current size.  The generated ViewHostMsg_PaintRect message will
 // have the IS_RESIZE_ACK flag set. It also receives the resizer rect so that
 // we don't have to fetch it every time WebKit asks for it.
-IPC_MESSAGE_ROUTED3(ViewMsg_Resize,
+IPC_MESSAGE_ROUTED4(ViewMsg_Resize,
                     gfx::Size /* new_size */,
+                    gfx::Size /* physical_backing_size */,
                     gfx::Rect /* resizer_rect */,
                     bool /* is_fullscreen */)