Protect readystatechange event dispatch on XMLHttpRequest.

Source/core/xmlhttprequest/XMLHttpRequest.cpp

 /*
  *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
  *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
  *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 646 matching lines @@
         m_state = newState;
         dispatchReadyStateChangeEvent();
     }
 }
 
 void XMLHttpRequest::dispatchReadyStateChangeEvent()
 {
     if (!executionContext())
         return;
 
+    // We need this protection because dispatchReadyStateChangeEvent may
+    // dispatch multiple events.
+    ScopedEventDispatchProtect protect(&m_eventDispatchRecursionLevel);
     if (m_async || (m_state <= OPENED || m_state == DONE)) {
         TRACE_EVENT1("devtools.timeline", "XHRReadyStateChange", "data", InspectorXhrReadyStateChangeEvent::data(executionContext(), this));
         XMLHttpRequestProgressEventThrottle::DeferredEventAction action = XMLHttpRequestProgressEventThrottle::Ignore;
         if (m_state == DONE) {
             if (m_error)
                 action = XMLHttpRequestProgressEventThrottle::Clear;
             else
                 action = XMLHttpRequestProgressEventThrottle::Flush;
         }
         m_progressEventThrottle->dispatchReadyStateChangeEvent(Event::create(EventTypeNames::readystatechange), action);
@@ skipping 1185 matching lines @@
     visitor->trace(m_responseDocumentParser);
     visitor->trace(m_progressEventThrottle);
     visitor->trace(m_upload);
     visitor->trace(m_blobLoader);
     XMLHttpRequestEventTarget::trace(visitor);
     DocumentParserClient::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink