[ServiceWorker] Use BodyStreamBuffer as the body data of the Response object.

Source/modules/serviceworkers/FetchRequestData.h

 // 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.
 
 #ifndef FetchRequestData_h
 #define FetchRequestData_h
 
 #include "platform/heap/Handle.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/Referrer.h"
@@ skipping 66 matching lines @@
     void setMode(WebURLRequest::FetchRequestMode mode) { m_mode = mode; }
     WebURLRequest::FetchRequestMode mode() const { return m_mode; }
     void setCredentials(WebURLRequest::FetchCredentialsMode credentials) { m_credentials = credentials; }
     WebURLRequest::FetchCredentialsMode credentials() const { return m_credentials; }
     void setResponseTainting(Tainting tainting) { m_responseTainting = tainting; }
     Tainting tainting() const { return m_responseTainting; }
     FetchHeaderList* headerList() const { return m_headerList.get(); }
     void setHeaderList(FetchHeaderList* headerList) { m_headerList = headerList; }
     PassRefPtr<BlobDataHandle> blobDataHandle() const { return m_blobDataHandle; }
     void setBlobDataHandle(PassRefPtr<BlobDataHandle> blobHandle) { m_blobDataHandle = blobHandle; }
+    String contentType() const;
 
     void trace(Visitor*);
 
 private:
     FetchRequestData();
 
     AtomicString m_method;
     KURL m_url;
     Member<FetchHeaderList> m_headerList;
     RefPtr<BlobDataHandle> m_blobDataHandle;
@@ skipping 10 matching lines @@
     WebURLRequest::FetchCredentialsMode m_credentials;
     // FIXME: Support m_useURLCredentialsFlag;
     // FIXME: Support m_manualRedirectFlag;
     // FIXME: Support m_redirectCount;
     Tainting m_responseTainting;
 };
 
 } // namespace blink
 
 #endif // FetchRequestData_h