Fix the race condition between mac drawRect and toggling accelerated compositing

content/browser/renderer_host/render_widget_host_view_mac.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #pragma once
 
 #if defined(__OBJC__)
 
@@ skipping 313 matching lines @@
   // paint requests by expanding the invalid rect rather than actually painting.
   bool about_to_validate_and_paint_;
 
   scoped_ptr<BrowserAccessibilityManager> browser_accessibility_manager_;
 
   // This is true when we have already scheduled a call to
   // |-callSetNeedsDisplayInRect:| but it has not been fulfilled yet.  Used to
   // prevent us from scheduling multiple calls.
   bool call_set_needs_display_in_rect_pending_;
 
+  // Whether last rendered frame was accelerated.
+  bool last_frame_was_accelerated_;
+
   // The invalid rect that needs to be painted by callSetNeedsDisplayInRect.
   // This value is only meaningful when
   // |call_set_needs_display_in_rect_pending_| is true.
   NSRect invalid_rect_;
 
   // The time at which this view started displaying white pixels as a result of
   // not having anything to paint (empty backing store from renderer). This
   // value returns true for is_null() if we are not recording whiteout times.
   base::TimeTicks whiteout_start_time_;
 
@@ skipping 72 matching lines @@
 
 class RenderWidgetHostView;
 class RenderWidgetHost;
 
 namespace render_widget_host_view_mac {
 CONTENT_EXPORT RenderWidgetHostView* CreateRenderWidgetHostView(
     RenderWidgetHost* widget);
 }
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_