Remove the overflowchanged event with a runtime flag

Source/core/dom/Document.cpp

 /*
  * 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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 3831 matching lines @@
         addMutationEventListenerTypeIfEnabled(DOMNODEREMOVED_LISTENER);
     } else if (eventType == EventTypeNames::DOMNodeRemovedFromDocument) {
         UseCounter::count(*this, UseCounter::DOMNodeRemovedFromDocumentEvent);
         addMutationEventListenerTypeIfEnabled(DOMNODEREMOVEDFROMDOCUMENT_LISTENER);
     } else if (eventType == EventTypeNames::DOMNodeInsertedIntoDocument) {
         UseCounter::count(*this, UseCounter::DOMNodeInsertedIntoDocumentEvent);
         addMutationEventListenerTypeIfEnabled(DOMNODEINSERTEDINTODOCUMENT_LISTENER);
     } else if (eventType == EventTypeNames::DOMCharacterDataModified) {
         UseCounter::count(*this, UseCounter::DOMCharacterDataModifiedEvent);
         addMutationEventListenerTypeIfEnabled(DOMCHARACTERDATAMODIFIED_LISTENER);
-    } else if (eventType == EventTypeNames::overflowchanged) {
+    } else if (eventType == EventTypeNames::overflowchanged && RuntimeEnabledFeatures::overflowChangedEventEnabled()) {
         UseCounter::countDeprecation(*this, UseCounter::OverflowChangedEvent);
         addListenerType(OVERFLOWCHANGED_LISTENER);
     } else if (eventType == EventTypeNames::webkitAnimationStart || (RuntimeEnabledFeatures::cssAnimationUnprefixedEnabled() && eventType == EventTypeNames::animationstart)) {
         addListenerType(ANIMATIONSTART_LISTENER);
     } else if (eventType == EventTypeNames::webkitAnimationEnd || (RuntimeEnabledFeatures::cssAnimationUnprefixedEnabled() && eventType == EventTypeNames::animationend)) {
         addListenerType(ANIMATIONEND_LISTENER);
     } else if (eventType == EventTypeNames::webkitAnimationIteration || (RuntimeEnabledFeatures::cssAnimationUnprefixedEnabled() && eventType == EventTypeNames::animationiteration)) {
         addListenerType(ANIMATIONITERATION_LISTENER);
         if (view()) {
             // Need to re-evaluate time-to-effect-change for any running animations.
@@ skipping 1885 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif