[chromecast] Delete MediaMessageLoop.

chromecast/browser/cast_browser_main_parts.h

Index: chromecast/browser/cast_browser_main_parts.h
diff --git a/chromecast/browser/cast_browser_main_parts.h b/chromecast/browser/cast_browser_main_parts.h
index ef9f69e4bf30c8978c941cd37eb758a1402d46ab..869c76bf8c0741f71e7aec8d0edd8eb5496e7a2a 100644
--- a/chromecast/browser/cast_browser_main_parts.h
+++ b/chromecast/browser/cast_browser_main_parts.h
@@ -14,6 +14,7 @@
 
 namespace base {
 class SingleThreadTaskRunner;
+class Thread;
 }  // namespace base
 
 namespace net {
@@ -40,7 +41,7 @@ class CastBrowserMainParts : public content::BrowserMainParts {
                        URLRequestContextFactory* url_request_context_factory);
   ~CastBrowserMainParts() override;
 
-  scoped_refptr<base::SingleThreadTaskRunner> GetMediaTaskRunner() const;
+  scoped_refptr<base::SingleThreadTaskRunner> GetMediaTaskRunner();
 
 #if !defined(OS_ANDROID)
   media::MediaResourceTracker* media_resource_tracker();
@@ -65,6 +66,9 @@ class CastBrowserMainParts : public content::BrowserMainParts {
   std::unique_ptr<media::VideoPlaneController> video_plane_controller_;
 
 #if !defined(OS_ANDROID)
+  // CMA thread used by AudioManager, MojoRenderer, and MediaPipelineBackend.
+  std::unique_ptr<base::Thread> media_thread_;
+
   // Tracks usage of media resource by e.g. CMA pipeline, CDM.
   media::MediaResourceTracker* media_resource_tracker_;