Set the AudioManager factory before the browser main loop.

chromecast/browser/cast_content_browser_client_simple.cc

 // Copyright 2015 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 "chromecast/browser/cast_content_browser_client.h"
 
 #include "content/public/browser/browser_message_filter.h"
+#include "media/audio/audio_manager_factory.h"
 
 namespace chromecast {
 namespace shell {
 
 void CastContentBrowserClient::PlatformAppendExtraCommandLineSwitches(
     base::CommandLine* command_line) {
 }
 
 std::vector<scoped_refptr<content::BrowserMessageFilter>>
 CastContentBrowserClient::PlatformGetBrowserMessageFilters() {
   return std::vector<scoped_refptr<content::BrowserMessageFilter>>();
 }
 
+scoped_ptr<::media::AudioManagerFactory>
+CastContentBrowserClient::PlatformCreateAudioManagerFactory() {
+  // Return nullptr. The factory will not be set, and the statically linked
+  // implementation of AudioManager will be used.
+  return scoped_ptr<::media::AudioManagerFactory>();
+}
+
 }  // namespace shell
 }  // namespace chromecast