[Media>UI] Apply throttling if the notification is updated too frequently

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 313 matching lines @@
     RemovePlayer(observer, player_id);
     return;
   }
 
   // Otherwise, suspend the session.
   DCHECK(IsActive());
   OnSuspendInternal(SuspendType::CONTENT, State::SUSPENDED);
 }
 
 void MediaSessionImpl::Resume(SuspendType suspend_type) {
-  DCHECK(IsSuspended());
+  if (!IsSuspended())

[whywhat, 2017/04/20 19:34:59]

Why this change?

[Zhiqiang Zhang (Slow), 2017/04/20 21:40:44]

As we now throttle the notifications, the notification is more likely to be
out-of-sync with the latest info. Therefore the notification might send an
action that MediaSession no longer accepts.

+    return;
 
   if (suspend_type == SuspendType::UI) {
     MediaSessionUmaHelper::RecordMediaSessionUserAction(
         MediaSessionUmaHelper::MediaSessionUserAction::PlayDefault);
   }
 
   // When the resume requests comes from another source than system, audio focus
   // must be requested.
   if (suspend_type != SuspendType::SYSTEM) {
     // Request audio focus again in case we lost it because another app started
@@ skipping 420 matching lines @@
     if (!IsServiceActiveForRenderFrameHost(frame))
       continue;
     best_frame = frame;
     min_depth = depth;
   }
 
   return best_frame ? services_[best_frame] : nullptr;
 }
 
 }  // namespace content