Factor out AudioOutputDelegate from AudioRendererHost.

content/browser/audio_device_thread.cc

Index: content/browser/audio_device_thread.cc
diff --git a/content/browser/audio_device_thread.cc b/content/browser/audio_device_thread.cc
new file mode 100644
index 0000000000000000000000000000000000000000..74f19b60a91d141dedd15b481cf2e3ecca805e51
--- /dev/null
+++ b/content/browser/audio_device_thread.cc
@@ -0,0 +1,16 @@
+// Copyright 2016 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 "content/browser/audio_device_thread.h"
+
+namespace content {
+
+AudioDeviceThread::AudioDeviceThread() : thread_("AudioThread") {
+#if defined(OS_WIN)
+  thread_.init_com_with_mta(true);
+#endif
+  CHECK(thread_.Start());
+}
+
+}  // namespace content