Revert of [ServiceWorker] Make Response class better conformance with the spec.

Source/modules/serviceworkers/ResponseInit.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 ResponseInit_h
 #define ResponseInit_h
 
 #include "bindings/core/v8/Dictionary.h"
-#include "modules/serviceworkers/Headers.h"
+#include "modules/serviceworkers/HeaderMap.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 struct ResponseInit {
     ResponseInit()
         : status(200)
         , statusText("OK")
     {
     }
     explicit ResponseInit(const Dictionary& options)
         : status(200)
         , statusText("OK")
     {
         options.get("status", status);
         // FIXME: Spec uses ByteString for statusText. http://crbug.com/347426
         options.get("statusText", statusText);
         options.get("headers", headers);
-        if (!headers) {
-            options.get("headers", headersDictionary);
-        }
     }
 
     unsigned short status;
     String statusText;
-    RefPtr<Headers> headers;
-    Dictionary headersDictionary;
+    RefPtr<HeaderMap> headers;
 };
 
 }
 
 #endif // ResponseInit_h