Replace MessageLoopProxy with SingleThreadTaskRunner for the rest of media/.

media/audio/scoped_task_runner_observer.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 MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
+#define MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+class WaitableEvent;
+}
+
+namespace media {
+
+// A common base class for AudioOutputDevice and AudioInputDevice that manages
+// a task runner and monitors it for destruction. If the object goes out of
+// scope before the task runner, the object will automatically remove itself
+// from the task runner's list of destruction observers.
+// NOTE: The class that inherits from this class must implement the
+// WillDestroyCurrentMessageLoop virtual method from DestructionObserver.
+class ScopedTaskRunnerObserver
+    : public base::MessageLoop::DestructionObserver {
+ public:
+  explicit ScopedTaskRunnerObserver(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
+
+ protected:
+  virtual ~ScopedTaskRunnerObserver();
+
+  // Accessor to the loop that's used by the derived class.
+  const scoped_refptr<base::SingleThreadTaskRunner>& task_runner() {
+    return task_runner_;
+  }
+
+ private:
+  // Call to add or remove ourselves from the list of destruction observers for
+  // the message loop.
+  void ObserveLoopDestruction(bool enable, base::WaitableEvent* done);
+
+  // A pointer to the task runner. In case it gets destroyed before this object
+  // goes out of scope, PostTask() etc will fail but not crash.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTaskRunnerObserver);
+};
+
+}  // namespace media.
+
+#endif  // MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_