Remove the (already disabled) OverflowChangedEvent runtime flag

Source/web/WebDOMEvent.cpp

 /*
  * Copyright (C) 2010 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
@@ skipping 147 matching lines @@
     ASSERT(m_private.get());
     return m_private->hasInterface(EventNames::WheelEvent);
 }
 
 bool WebDOMEvent::isBeforeTextInsertedEvent() const
 {
     ASSERT(m_private.get());
     return m_private->isBeforeTextInsertedEvent();
 }
 
-bool WebDOMEvent::isOverflowEvent() const
-{
-    ASSERT(m_private.get());
-    return m_private->hasInterface(EventNames::OverflowEvent);
-}
-
 bool WebDOMEvent::isPageTransitionEvent() const
 {
     ASSERT(m_private.get());
     return m_private->hasInterface(EventNames::PageTransitionEvent);
 }
 
 bool WebDOMEvent::isPopStateEvent() const
 {
     ASSERT(m_private.get());
     return m_private->hasInterface(EventNames::PopStateEvent);
 }
 
 bool WebDOMEvent::isProgressEvent() const
 {
     ASSERT(m_private.get());
     return m_private->hasInterface(EventNames::ProgressEvent);
 }
 
 bool WebDOMEvent::isXMLHttpRequestProgressEvent() const
 {
     ASSERT(m_private.get());
     return m_private->hasInterface(EventNames::XMLHttpRequestProgressEvent);
 }
 
 } // namespace blink