Remove code only used by Mac single threaded compositing.

content/browser/renderer_host/render_widget_host_view_guest.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 "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "content/browser/browser_plugin/browser_plugin_guest.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
@@ skipping 453 matching lines @@
 }
 
 bool RenderWidgetHostViewGuest::IsSpeaking() const {
   return platform_view_->IsSpeaking();
 }
 
 void RenderWidgetHostViewGuest::StopSpeaking() {
   platform_view_->StopSpeaking();
 }
 
-void RenderWidgetHostViewGuest::AboutToWaitForBackingStoreMsg() {
-  NOTREACHED();
-}
-
 bool RenderWidgetHostViewGuest::PostProcessEventForPluginIme(
     const NativeWebKeyboardEvent& event) {
   return false;
 }
 
 #endif  // defined(OS_MACOSX)
 
 #if defined(OS_ANDROID)
 void RenderWidgetHostViewGuest::ShowDisambiguationPopup(
     const gfx::Rect& target_rect,
@@ skipping 102 matching lines @@
     return;
   for (ui::GestureRecognizer::Gestures::iterator g_it = gestures->begin();
       g_it != gestures->end();
       ++g_it) {
     ForwardGestureEventToRenderer(*g_it);
   }
 }
 
 
 }  // namespace content