XMLHttpRequest should clear the response encoding when it clears responseText.

Source/core/xml/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 813 matching lines @@
 
 void XMLHttpRequest::clearResponse()
 {
     m_response = ResourceResponse();
     clearResponseBuffers();
 }
 
 void XMLHttpRequest::clearResponseBuffers()
 {
     m_responseText.clear();
+    m_responseEncoding = String();
     m_createdDocument = false;
     m_responseDocument = 0;
     m_responseBlob = 0;
     m_binaryResponseBuilder.clear();
     m_responseArrayBuffer.clear();
 }
 
 void XMLHttpRequest::clearRequest()
 {
     m_requestHeaders.clear();
@@ skipping 231 matching lines @@
 
     if (m_decoder)
         m_responseText = m_responseText.concatenateWith(m_decoder->flush());
 
     InspectorInstrumentation::didFinishXHRLoading(scriptExecutionContext(), this, identifier, m_responseText, m_url, m_lastSendURL, m_lastSendLineNumber);
 
     bool hadLoader = m_loader;
     m_loader = 0;
 
     changeState(DONE);
+    m_responseEncoding = String();
     m_decoder = 0;
 
     if (hadLoader)
         dropProtection();
 }
 
 void XMLHttpRequest::didSendData(unsigned long long bytesSent, unsigned long long totalBytesToBeSent)
 {
     if (!m_upload)
         return;
@@ skipping 147 matching lines @@
 {
     return &m_eventTargetData;
 }
 
 EventTargetData* XMLHttpRequest::ensureEventTargetData()
 {
     return &m_eventTargetData;
 }
 
 } // namespace WebCore