Split Dictionary's get and convert into DictionaryHelper.

Source/modules/serviceworkers/RequestInit.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 RequestInit_h
 #define RequestInit_h
 
 #include "bindings/core/v8/Dictionary.h"
 #include "modules/serviceworkers/Headers.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 struct RequestInit {
     explicit RequestInit(const Dictionary& options)
     {
-        options.get("method", method);
-        options.get("headers", headers);
+        DictionaryHelper::get(options, "method", method);
+        DictionaryHelper::get(options, "headers", headers);
         if (!headers) {
-            options.get("headers", headersDictionary);
+            DictionaryHelper::get(options, "headers", headersDictionary);
         }
-        options.get("mode", mode);
-        options.get("credentials", credentials);
+        DictionaryHelper::get(options, "mode", mode);
+        DictionaryHelper::get(options, "credentials", credentials);
     }
 
     String method;
     RefPtr<Headers> headers;
     Dictionary headersDictionary;
     String mode;
     String credentials;
 };
 
 }
 
 #endif // RequestInit_h