Remove the (already disabled) OverflowChangedEvent runtime flag

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 637 matching lines @@
 
     // keep track of what types of event listeners are registered, so we don't
     // dispatch events unnecessarily
     enum ListenerType {
         DOMSUBTREEMODIFIED_LISTENER          = 1,
         DOMNODEINSERTED_LISTENER             = 1 << 1,
         DOMNODEREMOVED_LISTENER              = 1 << 2,
         DOMNODEREMOVEDFROMDOCUMENT_LISTENER  = 1 << 3,
         DOMNODEINSERTEDINTODOCUMENT_LISTENER = 1 << 4,
         DOMCHARACTERDATAMODIFIED_LISTENER    = 1 << 5,
-        OVERFLOWCHANGED_LISTENER             = 1 << 6,
-        ANIMATIONEND_LISTENER                = 1 << 7,
-        ANIMATIONSTART_LISTENER              = 1 << 8,
-        ANIMATIONITERATION_LISTENER          = 1 << 9,
-        TRANSITIONEND_LISTENER               = 1 << 10,
-        SCROLL_LISTENER                      = 1 << 12
-        // 4 bits remaining
+        ANIMATIONEND_LISTENER                = 1 << 6,
+        ANIMATIONSTART_LISTENER              = 1 << 7,
+        ANIMATIONITERATION_LISTENER          = 1 << 8,
+        TRANSITIONEND_LISTENER               = 1 << 9,
+        SCROLL_LISTENER                      = 1 << 10
+        // 5 bits remaining
     };
 
     bool hasListenerType(ListenerType listenerType) const { return (m_listenerTypes & listenerType); }
     void addListenerTypeIfNeeded(const AtomicString& eventType);
 
     bool hasMutationObserversOfType(MutationObserver::MutationType type) const
     {
         return m_mutationObserverTypes & type;
     }
     bool hasMutationObservers() const { return m_mutationObserverTypes; }
@@ skipping 755 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h