[Chromecast] Fix media session blocking tests.

content/browser/media/session/media_session_impl.cc

Index: content/browser/media/session/media_session_impl.cc
diff --git a/content/browser/media/session/media_session_impl.cc b/content/browser/media/session/media_session_impl.cc
index bedae34f22e869fb82ab0414fc1935706116fd5b..f966dde9c169aa81c6100d062d818d7a8441a798 100644
--- a/content/browser/media/session/media_session_impl.cc
+++ b/content/browser/media/session/media_session_impl.cc
@@ -92,7 +92,7 @@ MediaSessionImpl::~MediaSessionImpl() {
   DCHECK(pepper_players_.empty());
   DCHECK(one_shot_players_.empty());
   DCHECK(audio_focus_state_ == State::INACTIVE);
-  for (auto& observer : observers_)
+  for (auto& observer : observers())
     observer.MediaSessionDestroyed();
 }
 
@@ -110,23 +110,15 @@ void MediaSessionImpl::WebContentsDestroyed() {
   AbandonSystemAudioFocusIfNeeded();
 }
 
-void MediaSessionImpl::AddObserver(MediaSessionObserver* observer) {
-  observers_.AddObserver(observer);
-}
-
-void MediaSessionImpl::RemoveObserver(MediaSessionObserver* observer) {
-  observers_.RemoveObserver(observer);
-}
-
 void MediaSessionImpl::NotifyMediaSessionMetadataChange(
     const base::Optional<MediaMetadata>& metadata) {
-  for (auto& observer : observers_)
+  for (auto& observer : observers())
     observer.MediaSessionMetadataChanged(metadata);
 }
 
 void MediaSessionImpl::NotifyMediaSessionActionsChange(
     const std::set<blink::mojom::MediaSessionAction>& actions) {
-  for (auto& observer : observers_)
+  for (auto& observer : observers())
     observer.MediaSessionActionsChanged(actions);
 }
 
@@ -524,7 +516,7 @@ void MediaSessionImpl::NotifyAboutStateChange() {
   }
 
   media_session_state_listeners_.Notify(audio_focus_state_);
-  for (auto& observer : observers_)
+  for (auto& observer : observers())
     observer.MediaSessionStateChanged(IsControllable(), is_actually_suspended);
 }