[Fetch] Response.clone should tee the body stream.

Source/modules/fetch/Response.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/fetch/Response.h"
 
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/dom/DOMArrayBuffer.h"
@@ skipping 281 matching lines @@
 Response* Response::clone(ExceptionState& exceptionState)
 {
     if (bodyUsed()) {
         exceptionState.throwTypeError("Response body is already used");
         return nullptr;
     }
     if (streamAccessed()) {
         BodyStreamBuffer* drainingStream = createDrainingStream();
         m_response->replaceBodyStreamBuffer(drainingStream);
     }
+    // Lock the old body and set |body| property to the new one.
+    lockBody();
+    refreshBody();
+
     FetchResponseData* response = m_response->clone();
     Headers* headers = Headers::create(response->headerList());
     headers->setGuard(m_headers->guard());
     Response* r = new Response(executionContext(), response, headers);
     r->suspendIfNeeded();
     return r;
 }
 
 void Response::populateWebServiceWorkerResponse(WebServiceWorkerResponse& response)
 {
@@ skipping 55 matching lines @@
 }
 
 DEFINE_TRACE(Response)
 {
     Body::trace(visitor);
     visitor->trace(m_response);
     visitor->trace(m_headers);
 }
 
 } // namespace blink