InitEvent should not do anything if dispatch flag is set.

third_party/WebKit/Source/core/events/Event.h

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * 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.
@@ skipping 198 matching lines @@
     Event();
     Event(const AtomicString& type, bool canBubble, bool cancelable);
     Event(const AtomicString& type, bool canBubble, bool cancelable, EventTarget* relatedTarget);
     Event(const AtomicString& type, bool canBubble, bool cancelable, double platformTimeStamp);
     Event(const AtomicString& type, bool canBubble, bool cancelable, EventTarget* relatedTarget, double platformTimeStamp);
     Event(const AtomicString& type, bool canBubble, bool cancelable, bool scoped);
     Event(const AtomicString& type, bool canBubble, bool cancelable, bool scoped, bool relatedTargetScoped, double platformTimeStamp);
     Event(const AtomicString& type, const EventInit&);
 
     virtual void receivedTarget();
-    bool dispatched() const { return m_target; }
 
     void setCanBubble(bool bubble) { m_canBubble = bubble; }
 
 private:
     enum EventPathMode {
         EmptyAfterDispatch,
         NonEmptyAfterDispatch
     };
 
     HeapVector<Member<EventTarget>> pathInternal(ScriptState*, EventPathMode) const;
@@ skipping 23 matching lines @@
     // WebInputEvent instance.
     double m_platformTimeStamp;
 };
 
 #define DEFINE_EVENT_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName, Event, event, event->is##typeName(), event.is##typeName())
 
 } // namespace blink
 
 #endif // Event_h