Use a weak pointer to post service control events and session change notifications.

remoting/base/stoppable.h

-// 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 REMOTING_BASE_STOPPABLE_H_
-#define REMOTING_BASE_STOPPABLE_H_
-
-#include "base/basictypes.h"
-#include "base/callback.h"
-#include "base/memory/ref_counted.h"
-
-namespace base {
-class SingleThreadTaskRunner;
-}  // namespace base
-
-namespace remoting {
-
-// A helper base class that implements asynchronous shutdown on a specific
-// thread.
-class Stoppable {
- public:
-  // Constructs an object and stores the callback to be posted to |task_runner|
-  // once the object has been shutdown completely.
-  Stoppable(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-            const base::Closure& stopped_callback);
-  virtual ~Stoppable();
-
-  // Initiates shutdown. It can be called by both the owner of the object and
-  // the object itself resulting in the same shutdown sequence.
-  void Stop();
-
- protected:
-  // Called by derived classes to notify about shutdown completion. Posts
-  // the completion task on |task_runner_| message loop.
-  void CompleteStopping();
-
-  // Derived classes have to override this method to implement the shutdown
-  // logic.
-  virtual void DoStop() = 0;
-
-  enum State {
-    kRunning,
-    kStopping,
-    kStopped
-  };
-
-  State stoppable_state() const { return state_; }
-
- private:
-  State state_;
-
-  // A callback to be called when shutdown is completed.
-  base::Closure stopped_callback_;
-
-  // The target task runner where the shutdown notification will be posted.
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  DISALLOW_COPY_AND_ASSIGN(Stoppable);
-};
-
-}  // namespace remoting
-
-#endif  // REMOTING_BASE_STOPPABLE_H_