Revert of [chromecast] Pass media task runner to MediaPipelineBackendManager.

chromecast/browser/cast_browser_main_parts.cc

Index: chromecast/browser/cast_browser_main_parts.cc
diff --git a/chromecast/browser/cast_browser_main_parts.cc b/chromecast/browser/cast_browser_main_parts.cc
index 075521ddf35023465d27d6b8472e2887b6898787..5c3862b65cf2f3a976493bde29710310364e40b9 100644
--- a/chromecast/browser/cast_browser_main_parts.cc
+++ b/chromecast/browser/cast_browser_main_parts.cc
@@ -271,15 +271,6 @@
   }
   return media_resource_tracker_;
 }
-
-media::MediaPipelineBackendManager*
-CastBrowserMainParts::media_pipeline_backend_manager() {
-  if (!media_pipeline_backend_manager_) {
-    media_pipeline_backend_manager_.reset(
-        new media::MediaPipelineBackendManager(GetMediaTaskRunner()));
-  }
-  return media_pipeline_backend_manager_.get();
-}
 #endif
 
 void CastBrowserMainParts::PreMainMessageLoopStart() {
@@ -346,8 +337,7 @@
 
   // AudioManager is created immediately after threads are created, requiring
   // AudioManagerFactory to be set beforehand.
-  ::media::AudioManager::SetFactory(
-      new media::CastAudioManagerFactory(media_pipeline_backend_manager()));
+  ::media::AudioManager::SetFactory(new media::CastAudioManagerFactory());
 
   // Set GL strings so GPU config code can make correct feature blacklisting/
   // whitelisting decisions.
@@ -495,7 +485,6 @@
 #if !defined(OS_ANDROID)
   media_resource_tracker_->FinalizeAndDestroy();
   media_resource_tracker_ = nullptr;
-  media_pipeline_backend_manager_.reset();
 #endif
 }