Don't expect ack for ViewMsg_OnResize if backing size is empty

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 516 matching lines @@
       was_fullscreen != is_fullscreen_ ||
       old_overdraw_bottom_height != overdraw_bottom_height_;
 
   if (!size_changed && !side_payload_changed)
     return;
 
   if (in_flight_size_ != gfx::Size() && new_size == in_flight_size_ &&
       !side_payload_changed)
     return;
 
-  // We don't expect to receive an ACK when the requested size is empty or when
-  // the main viewport size didn't change.
-  if (!new_size.IsEmpty() && size_changed)
+  // We don't expect to receive an ACK when the requested size or the physical
+  // backing size is empty, or when the main viewport size didn't change.
+  if (!new_size.IsEmpty() && !physical_backing_size_.IsEmpty() && size_changed)
     resize_ack_pending_ = true;
 
   if (!Send(new ViewMsg_Resize(routing_id_, new_size, physical_backing_size_,
                                overdraw_bottom_height_,
                                GetRootWindowResizerRect(), is_fullscreen_))) {
     resize_ack_pending_ = false;
   } else {
     in_flight_size_ = new_size;
   }
 }
@@ skipping 1919 matching lines @@
 }
 
 void RenderWidgetHostImpl::DetachDelegate() {
   delegate_ = NULL;
 }
 
 void RenderWidgetHostImpl::FrameSwapped(const cc::LatencyInfo& latency_info) {
 }
 
 }  // namespace content