[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/modules/v8/RequestOrUSVString.h"
 #include "modules/ModulesExport.h"
@@ skipping 76 matching lines @@
   Request(ScriptState*, FetchRequestData*, Headers*);
   Request(ScriptState*, FetchRequestData*);
 
   const FetchRequestData* GetRequest() const { return request_; }
   static Request* CreateRequestWithRequestOrString(ScriptState*,
                                                    Request*,
                                                    const String&,
                                                    RequestInit&,
                                                    ExceptionState&);
 
+  String ContentType() const override;
   String MimeType() const override;
   void RefreshBody(ScriptState*);
 
   const Member<FetchRequestData> request_;
   const Member<Headers> headers_;
 };
 
 }  // namespace blink
 
 #endif  // Request_h