InitEvent should not do anything if dispatch flag is set.

third_party/WebKit/Source/core/events/CustomEvent.cpp

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 32 matching lines @@
 {
 }
 
 void CustomEvent::initCustomEvent(const AtomicString& type, bool canBubble, bool cancelable, const ScriptValue&)
 {
     initEvent(type, canBubble, cancelable);
 }
 
 void CustomEvent::initCustomEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<SerializedScriptValue> serializedDetail)
 {
-    if (dispatched())
+    if (isBeingDispatched())
         return;
 
     initEvent(type, canBubble, cancelable);
 
     m_serializedDetail = serializedDetail;
 }
 
 const AtomicString& CustomEvent::interfaceName() const
 {
     return EventNames::CustomEvent;
 }
 
 DEFINE_TRACE(CustomEvent)
 {
     Event::trace(visitor);
 }
 
 } // namespace blink