Revert 138216 - [Sync] Turn notifier::PushClient into an interface

jingle/notifier/listener/push_client_observer.h

Index: jingle/notifier/listener/push_client_observer.h
===================================================================
--- jingle/notifier/listener/push_client_observer.h	(revision 138220)
+++ jingle/notifier/listener/push_client_observer.h	(working copy)
@@ -1,32 +0,0 @@
-// Copyright (c) 2012 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 JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_OBSERVER_H_
-#define JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_OBSERVER_H_
-
-#include "jingle/notifier/listener/notification_defines.h"
-
-namespace notifier {
-
-// A PushClientObserver is notified whenever an incoming notification
-// is received or when the state of the push client changes.
-class PushClientObserver {
- protected:
-  virtual ~PushClientObserver();
-
- public:
-  // Called when the state of the push client changes.  If
-  // |notifications_enabled| is true, that means notifications can be
-  // sent and received freely.  If it is false, that means no
-  // notifications can be sent or received.
-  virtual void OnNotificationStateChange(bool notifications_enabled) = 0;
-
-  // Called when a notification is received.  The details of the
-  // notification are in |notification|.
-  virtual void OnIncomingNotification(const Notification& notification) = 0;
-};
-
-}  // namespace notifier
-
-#endif  // JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_OBSERVER_H_