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

Source/modules/serviceworkers/HeaderMap.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 HeaderMap_h
-#define HeaderMap_h
-
-#include "bindings/core/v8/ScriptWrappable.h"
-#include "wtf/Forward.h"
-#include "wtf/HashMap.h"
-#include "wtf/RefCounted.h"
-#include "wtf/text/StringHash.h"
-
-namespace WebCore {
-
-class HeaderMapForEachCallback;
-class ScriptValue;
-
-class HeaderMap FINAL : public ScriptWrappable, public RefCounted<HeaderMap> {
-public:
-    static PassRefPtr<HeaderMap> create();
-    static PassRefPtr<HeaderMap> create(const HashMap<String, String>& headers);
-
-    // HeaderMap.idl implementation.
-    unsigned long size() const;
-    void clear();
-    bool remove(const String& key);
-    String get(const String& key);
-    bool has(const String& key);
-    void set(const String& key, const String& value);
-    void forEach(PassOwnPtr<HeaderMapForEachCallback>, ScriptValue&);
-    void forEach(PassOwnPtr<HeaderMapForEachCallback>);
-
-    const HashMap<String, String>& headerMap() const { return m_headers; }
-
-private:
-    HeaderMap();
-    explicit HeaderMap(const HashMap<String, String>& headers);
-    void forEachInternal(PassOwnPtr<HeaderMapForEachCallback>, ScriptValue* thisArg);
-
-    // FIXME: this doesn't preserve ordering while ES6 Map type requires it.
-    HashMap<String, String> m_headers;
-};
-
-} // namespace WebCore
-
-#endif // HeaderMap_h