Remove support for the externalResourcesRequired attribute.

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 2327 matching lines @@
     if (f && f->script().canExecuteScripts(NotAboutToExecuteScript)) {
         ImageLoader::dispatchPendingBeforeLoadEvents();
         ImageLoader::dispatchPendingLoadEvents();
         ImageLoader::dispatchPendingErrorEvents();
 
         HTMLLinkElement::dispatchPendingLoadEvents();
         HTMLStyleElement::dispatchPendingLoadEvents();
     }
 
     // To align the HTML load event and the SVGLoad event for the outermost <svg> element, fire it from
-    // here, instead of doing it from SVGElement::finishedParsingChildren (if externalResourcesRequired="false",
-    // which is the default, for ='true' its fired at a later time, once all external resources finished loading).
+    // here, instead of doing it from SVGElement::finishedParsingChildren.
     if (svgExtensions())
         accessSVGExtensions()->dispatchSVGLoadEventToOutermostSVGElements();
 
     dispatchWindowLoadEvent();
     enqueuePageshowEvent(PageshowEventNotPersisted);
     enqueuePopstateEvent(m_pendingStateObject ? m_pendingStateObject.release() : SerializedScriptValue::nullValue());
 
     if (frame()) {
         frame()->loader().client()->dispatchDidHandleOnloadEvents();
         loader()->applicationCacheHost()->stopDeferringEvents();
@@ skipping 2994 matching lines @@
 void Document::modifiedStyleSheet(StyleSheet* sheet, RecalcStyleTime when, StyleResolverUpdateMode updateMode)
 {
     if (!isActive())
         return;
 
     styleEngine()->modifiedStyleSheet(sheet);
     styleResolverChanged(when, updateMode);
 }
 
 } // namespace WebCore