Vibration cannot be canceled during pattern vibration.

Source/modules/vibration/NavigatorVibration.h

 /*
  *  Copyright (C) 2012 Samsung Electronics
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 34 matching lines @@
     void timerStopFired(Timer<NavigatorVibration>*);
 
     // Inherited from PageLifecycleObserver
     virtual void pageVisibilityChanged() OVERRIDE;
     virtual void didCommitLoad(Frame*) OVERRIDE;
 
     static bool vibrate(Navigator*, unsigned time);
     static bool vibrate(Navigator*, const VibrationPattern&);
     static NavigatorVibration* from(Page*);
 
+    bool isVibrating() const { return m_isVibrating; }
+
 private:
     explicit NavigatorVibration(Page*);
     static const char* supplementName();
 
     Timer<NavigatorVibration> m_timerStart;
     Timer<NavigatorVibration> m_timerStop;
     bool m_isVibrating;
     VibrationPattern m_pattern;
 };
 
 } // namespace WebCore
 
 #endif // NavigatorVibration_h