Prevent entering XHR methods while loader is being cancelled.

Source/core/xml/XMLHttpRequest.h

 /*
  *  Copyright (C) 2003, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005, 2006 Alexey Proskuryakov <ap@nypop.com>
  *  Copyright (C) 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
  *  version 2 of the License, or (at your option) any later version.
@@ skipping 91 matching lines @@
     void open(const String& method, const KURL&, bool async, ExceptionState&);
     void open(const String& method, const KURL&, bool async, const String& user, ExceptionState&);
     void open(const String& method, const KURL&, bool async, const String& user, const String& password, ExceptionState&);
     void send(ExceptionState&);
     void send(Document*, ExceptionState&);
     void send(const String&, ExceptionState&);
     void send(Blob*, ExceptionState&);
     void send(DOMFormData*, ExceptionState&);
     void send(ArrayBuffer*, ExceptionState&);
     void send(ArrayBufferView*, ExceptionState&);
-    void abort();
+    void abort(ExceptionState&);
     void setRequestHeader(const AtomicString& name, const String& value, ExceptionState&);
     void overrideMimeType(const String& override);
     String getAllResponseHeaders(ExceptionState&) const;
     String getResponseHeader(const AtomicString& name, ExceptionState&) const;
     ScriptString responseText(ExceptionState&);
     ScriptString responseJSONSource();
     Document* responseXML(ExceptionState&);
     Blob* responseBlob();
     Stream* responseStream();
     unsigned long timeout() const { return m_timeoutMilliseconds; }
@@ skipping 86 matching lines @@
 
     RefPtr<TextResourceDecoder> m_decoder;
 
     ScriptString m_responseText;
     mutable bool m_createdDocument;
     mutable RefPtr<Document> m_responseDocument;
 
     RefPtr<SharedBuffer> m_binaryResponseBuilder;
     mutable RefPtr<ArrayBuffer> m_responseArrayBuffer;
 
+    // Prevents reentrant of methods while m_loader->cancel() is running.
+    bool m_preventReentrant;
+
     bool m_error;
 
     bool m_uploadEventsAllowed;
     bool m_uploadComplete;
 
     bool m_sameOriginRequest;
 
     // Used for onprogress tracking
     long long m_receivedLength;
 
     unsigned m_lastSendLineNumber;
     String m_lastSendURL;
     ExceptionCode m_exceptionCode;
 
     XMLHttpRequestProgressEventThrottle m_progressEventThrottle;
 
     // An enum corresponding to the allowed string values for the responseType attribute.
     ResponseTypeCode m_responseTypeCode;
     Timer<XMLHttpRequest> m_protectionTimer;
     RefPtr<SecurityOrigin> m_securityOrigin;
 };
 
 } // namespace WebCore
 
 #endif // XMLHttpRequest_h