Plumb physical backing size from RWHV to renderer CC.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 4ab00592b90b294893bb3efde5fe50fdad5c9f40..1d3313d20caf01d46cc22a7e62fd1890dfe4e524 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -690,6 +690,9 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // The current size of the RenderWidget.
   gfx::Size current_size_;
 
+  // The size of the view's backing surface in non-DPI-adjusted pixels.
+  gfx::Size physical_backing_size_;
+
   // The size we last sent as requested size to the renderer. |current_size_|
   // is only updated once the resize message has been ack'd. This on the other
   // hand is updated when the resize message is sent. This is very similar to