[webnfc] Implement push() method in blink nfc module.

third_party/WebKit/public/platform/modules/nfc/WebNFCObserver.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 WebNFCObserver_h
-#define WebNFCObserver_h
-
-namespace blink {
-
-struct WebNFCMessage;
-
-// Observer interface that should be implemented in order to get notification
-// about triggered NFC watch.
-class WebNFCObserver {
-public:
-    virtual ~WebNFCObserver() { }
-
-    // The id is an identifier of the registered NFC watch that was obtained after
-    // calling watch method (https://w3c.github.io/web-nfc/#the-watch-method).
-    // The WebNFCMessage that matches NFC watch filtering criteria is provided to the callback.
-    // See https://w3c.github.io/web-nfc/#idl-def-messagecallback
-    virtual void onWatch(long id, const WebNFCMessage&) = 0;
-};
-
-} // namespace blink
-
-#endif // WebNFCObserver_h