[webnfc] Align NFC interface with latest specification.

third_party/WebKit/Source/modules/nfc/MessageCallback.h

+// Copyright 2015 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 MessageCallback_h
+#define MessageCallback_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class NFCMessage;
+
+class MessageCallback : public GarbageCollectedFinalized<MessageCallback> {
+public:
+    virtual ~MessageCallback() { }
+    DEFINE_INLINE_VIRTUAL_TRACE() { }
+    virtual void handleMessage(const NFCMessage&) = 0;
+};
+
+} // namespace blink
+
+#endif // MessageCallback_h