Split Dictionary's get and convert into DictionaryHelper.

Source/bindings/core/v8/DictionaryHelper.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 DictionaryHelper_h
+#define DictionaryHelper_h
+
+#include "bindings/core/v8/Dictionary.h"
+
+namespace WebCore {
+
+struct DictionaryHelper {
+    template <typename T>
+    static bool get(const Dictionary&, const String& key, T& value);
+    template <typename T>
+    static bool get(const Dictionary&, const String& key, T& value, bool& hasValue);
+    template <typename T>
+    static bool convert(const Dictionary&, Dictionary::ConversionContext&, const String& key, T& value);
+};
+
+} // namespace WebCore
+
+#endif