[Fetch API] Implement Request.formData and Response.formData.

third_party/WebKit/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/RequestOrUSVString.h"
@@ skipping 75 matching lines @@
   Request(ScriptState*, FetchRequestData*, Headers*);
   Request(ScriptState*, FetchRequestData*);
 
   const FetchRequestData* request() const { return m_request; }
   static Request* createRequestWithRequestOrString(ScriptState*,
                                                    Request*,
                                                    const String&,
                                                    RequestInit&,
                                                    ExceptionState&);
 
+  String contentType() const override;
   String mimeType() const override;
   void refreshBody(ScriptState*);
 
   const Member<FetchRequestData> m_request;
   const Member<Headers> m_headers;
 };
 
 }  // namespace blink
 
 #endif  // Request_h