Replace MessageLoopProxy with SingleThreadTaskRunner for the rest of media/.

media/audio/scoped_loop_observer.cc

-// 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.
-
-#include "media/audio/scoped_loop_observer.h"
-
-#include "base/bind.h"
-#include "base/synchronization/waitable_event.h"
-
-namespace media {
-
-ScopedLoopObserver::ScopedLoopObserver(
-    const scoped_refptr<base::MessageLoopProxy>& loop)
-    : loop_(loop) {
-  ObserveLoopDestruction(true, NULL);
-}
-
-ScopedLoopObserver::~ScopedLoopObserver() {
-  ObserveLoopDestruction(false, NULL);
-}
-
-void ScopedLoopObserver::ObserveLoopDestruction(bool enable,
-                                                base::WaitableEvent* done) {
-  // Note: |done| may be NULL.
-  if (loop_->BelongsToCurrentThread()) {
-    base::MessageLoop* loop = base::MessageLoop::current();
-    if (enable) {
-      loop->AddDestructionObserver(this);
-    } else {
-      loop->RemoveDestructionObserver(this);
-    }
-  } else {
-    base::WaitableEvent event(false, false);
-    if (loop_->PostTask(FROM_HERE,
-            base::Bind(&ScopedLoopObserver::ObserveLoopDestruction,
-                       base::Unretained(this), enable, &event))) {
-      event.Wait();
-    } else {
-      // The message loop's thread has already terminated, so no need to wait.
-    }
-  }
-
-  if (done)
-    done->Signal();
-}
-
-}  // namespace media.