Share one thread between all AudioOutputControllers instead of creating one per stream.

media/audio/audio_manager_base.cc

+// Copyright (c) 2010 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/audio_manager_base.h"
+
+AudioManagerBase::AudioManagerBase()
+    : audio_thread_("AudioThread"),
+      initialized_(false) {
+}
+
+void AudioManagerBase::Init() {
+  initialized_ = audio_thread_.Start();
+}
+
+MessageLoop* AudioManagerBase::GetMessageLoop() {
+  DCHECK(initialized_);
+  return audio_thread_.message_loop();
+}