MediaSession: Stop observers on MediaSession destruction

content/browser/media/session/media_session_impl.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 "content/browser/media/session/media_session_impl.h"
 
 #include <algorithm>
 #include "content/browser/media/session/audio_focus_delegate.h"
 #include "content/browser/media/session/media_session_controller.h"
 #include "content/browser/media/session/media_session_player_observer.h"
@@ skipping 75 matching lines @@
     session->Initialize();
   }
   return session;
 }
 
 MediaSessionImpl::~MediaSessionImpl() {
   DCHECK(normal_players_.empty());
   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();
+    observer.StopObserving();
+  }
 }
 
 void MediaSessionImpl::WebContentsDestroyed() {
   // This should only work for tests. In production, all the players should have
   // already been removed before WebContents is destroyed.
 
   // TODO(zqzhang): refactor MediaSessionImpl, maybe move the interface used to
   // talk with AudioFocusManager out to a seperate class. The AudioFocusManager
   // unit tests then could mock the interface and abandon audio focus when
   // WebContents is destroyed. See https://crbug.com/651069
@@ skipping 614 matching lines @@
     if (!IsServiceActiveForRenderFrameHost(frame))
       continue;
     best_frame = frame;
     min_depth = depth;
   }
 
   return best_frame ? services_[best_frame] : nullptr;
 }
 
 }  // namespace content