Ensures that audio tasks cannot run after AudioManager is deleted.

chromecast/browser/cast_content_browser_client.cc

Index: chromecast/browser/cast_content_browser_client.cc
diff --git a/chromecast/browser/cast_content_browser_client.cc b/chromecast/browser/cast_content_browser_client.cc
index c7e9033b501bec54fb8b4b6ea231ffec28c0342c..c90a40cf8b2d6e51b8492e6c91db2e3e255ce722 100644
--- a/chromecast/browser/cast_content_browser_client.cc
+++ b/chromecast/browser/cast_content_browser_client.cc
@@ -191,11 +191,14 @@ CastContentBrowserClient::media_pipeline_backend_manager() {
   return cast_browser_main_parts_->media_pipeline_backend_manager();
 }
 
-::media::ScopedAudioManagerPtr CastContentBrowserClient::CreateAudioManager(
+std::unique_ptr<::media::AudioManager>
+CastContentBrowserClient::CreateAudioManager(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
     ::media::AudioLogFactory* audio_log_factory) {
-  return ::media::ScopedAudioManagerPtr(new media::CastAudioManager(
-      GetMediaTaskRunner(), GetMediaTaskRunner(), audio_log_factory,
-      media_pipeline_backend_manager()));
+  return base::MakeUnique<media::CastAudioManager>(
+      task_runner, worker_task_runner, audio_log_factory,
+      media_pipeline_backend_manager());
 }
 
 std::unique_ptr<::media::CdmFactory>