Fix a race condition in canvas hibernation when visibility is toggled repeatedly

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 144 matching lines @@
     size_t m_bytesAllocated;
     bool m_haveRecordedDrawCommands;
     bool m_destructionInProgress;
     SkFilterQuality m_filterQuality;
     bool m_isHidden;
     bool m_isDeferralEnabled;
     bool m_isRegisteredTaskObserver;
     bool m_renderingTaskCompletedForCurrentFrame;
     bool m_softwareRenderingWhileHidden;
     bool m_surfaceCreationFailedAtLeastOnce = false;
+    bool m_hibernationScheduled = false;
 
     friend class Canvas2DLayerBridgeTest;
 
     struct MailboxInfo {
         DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
         WebExternalTextureMailbox m_mailbox;
         RefPtr<SkImage> m_image;
         RefPtr<Canvas2DLayerBridge> m_parentLayerBridge;
 
         MailboxInfo(const MailboxInfo&);
@@ skipping 12 matching lines @@
     GLenum m_lastFilter;
     AccelerationMode m_accelerationMode;
     OpacityMode m_opacityMode;
     IntSize m_size;
     int m_recordingPixelCount;
 };
 
 } // namespace blink
 
 #endif