Implementation of device metrics emulation in render view.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
===================================================================
--- content/browser/renderer_host/render_widget_host_view_aura.h	(revision 221161)
+++ content/browser/renderer_host/render_widget_host_view_aura.h	(working copy)
@@ -224,6 +224,7 @@
   virtual gfx::Rect GetBoundsInRootWindow() OVERRIDE;
   virtual void GestureEventAck(int gesture_event_type,
                                InputEventAckState ack_result) OVERRIDE;
+  virtual void SetExpectedRenderedSize(const gfx::Size& size) OVERRIDE;
   virtual void ProcessAckedTouchEvent(
       const TouchEventWithLatencyInfo& touch,
       InputEventAckState ack_result) OVERRIDE;
@@ -636,6 +637,10 @@
   // renderer of producing a frame of the right size.
   scoped_ptr<ResizeLock> resize_lock_;
 
+  // When emulating device metrics, renderer may supply image of different size.
+  // Empty size means the default view size is expected.
+  gfx::Size expected_rendered_size_;
+
   // Keeps track of the current frame size.
   gfx::Size current_frame_size_;