Cleanup: Add more conversion helpers for usage.

Source/core/events/GestureEvent.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:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 55 matching lines @@
 private:
     explicit GestureEventDispatchMediator(PassRefPtr<GestureEvent>);
 
     GestureEvent* event() const;
 
     virtual bool dispatchEvent(EventDispatcher*) const OVERRIDE;
 };
 
 inline GestureEvent* toGestureEvent(Event* event)
 {
-    ASSERT(event && event->isGestureEvent());
+    ASSERT_WITH_SECURITY_IMPLICATION(!event || event->isGestureEvent());
     return static_cast<GestureEvent*>(event);
 }
 
 } // namespace WebCore
 
 #endif // GestureEvent_h