Change BodyStreamBuffer to be FetchDataConsumerHandle-based and enable backpressure in Fetch API

Source/modules/fetch/Request.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 Request_h
 #define Request_h
 
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "bindings/modules/v8/UnionTypesModules.h"
@@ skipping 35 matching lines @@
     // From Request.idl:
     String method() const;
     KURL url() const;
     Headers* headers() const { return m_headers; }
     String context() const;
     String referrer() const;
     String mode() const;
     String credentials() const;
 
     // From Request.idl:
-    Request* clone(ExceptionState&) const;
+    Request* clone(ExceptionState&);
 
     FetchRequestData* passRequestData();
 
     void populateWebServiceWorkerRequest(WebServiceWorkerRequest&) const;
 
-    void setBodyBlobHandle(PassRefPtr<BlobDataHandle>);
-    bool hasBody() const { return m_request->blobDataHandle(); }
+    bool hasBody() const { return m_request->buffer(); }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     Request(ExecutionContext*, FetchRequestData*);
     Request(ExecutionContext*, const WebServiceWorkerRequest&);
     Request(ExecutionContext*, FetchRequestData*, Headers*);
 
+    void setBuffer(BodyStreamBuffer*);
+    void refreshBody();
+
     static Request* createRequestWithRequestOrString(ScriptState*, Request*, const String&, const RequestInit&, ExceptionState&);
     void clearHeaderList();
 
-    PassRefPtr<BlobDataHandle> blobDataHandle() const override;
-    BodyStreamBuffer* buffer() const override;
     String mimeType() const override;
 
     const Member<FetchRequestData> m_request;
     const Member<Headers> m_headers;
 };
 
 } // namespace blink
 
 #endif // Request_h