Explicitly unregister from receiving notifications before releasing the webrtc mediastream observer.

BUG=430699

Review URL: https://codereview.chromium.org/703033004

Cr-Commit-Position: refs/heads/master@{#303006}

2 files changed, 17 insertions, 4 deletions

diff --git a/content/renderer/media/remote_media_stream_impl.cc b/content/renderer/media/remote_media_stream_impl.cc
index 057c104..06f4177 100644
--- a/content/renderer/media/remote_media_stream_impl.cc
+++ b/content/renderer/media/remote_media_stream_impl.cc
@@ -328,8 +328,7 @@ RemoteMediaStreamImpl::Observer::Observer(
 }
 
 RemoteMediaStreamImpl::Observer::~Observer() {
-  DCHECK(ctor_thread_.CalledOnValidThread());
-  webrtc_stream_->UnregisterObserver(this);
+  DCHECK(!webrtc_stream_.get()) << "Unregister hasn't been called";
 }
 
 void RemoteMediaStreamImpl::Observer::InitializeOnMainThread(
@@ -339,6 +338,14 @@ void RemoteMediaStreamImpl::Observer::InitializeOnMainThread(
     media_stream_->InitializeOnMainThread(label);
 }
 
+void RemoteMediaStreamImpl::Observer::Unregister() {
+  DCHECK(main_thread_->BelongsToCurrentThread());
+  webrtc_stream_->UnregisterObserver(this);
+  // Since we're guaranteed to not get further notifications, it's safe to
+  // release the webrtc_stream_ here.
+  webrtc_stream_ = nullptr;
+}
+
 void RemoteMediaStreamImpl::Observer::OnChanged() {
   scoped_ptr<RemoteAudioTrackAdapters> audio(new RemoteAudioTrackAdapters());
   scoped_ptr<RemoteVideoTrackAdapters> video(new RemoteVideoTrackAdapters());
@@ -383,6 +390,7 @@ RemoteMediaStreamImpl::~RemoteMediaStreamImpl() {
   DCHECK(observer_->main_thread()->BelongsToCurrentThread());
   for (auto& track : audio_track_observers_)
     track->Unregister();
+  observer_->Unregister();
 }
 
 void RemoteMediaStreamImpl::InitializeOnMainThread(const std::string& label) {
diff --git a/content/renderer/media/remote_media_stream_impl.h b/content/renderer/media/remote_media_stream_impl.h
index 683804a..0c230ba 100644
--- a/content/renderer/media/remote_media_stream_impl.h
+++ b/content/renderer/media/remote_media_stream_impl.h
@@ -65,6 +65,12 @@ class CONTENT_EXPORT RemoteMediaStreamImpl {
 
     void InitializeOnMainThread(const std::string& label);
 
+    // Uninitializes the observer, unregisteres from receiving notifications
+    // and releases the webrtc stream.
+    // Note: Must be called from the main thread before releasing the main
+    // reference.
+    void Unregister();
+
    private:
     friend class base::RefCountedThreadSafe<Observer>;
     ~Observer() override;
@@ -78,8 +84,7 @@ class CONTENT_EXPORT RemoteMediaStreamImpl {
 
     base::WeakPtr<RemoteMediaStreamImpl> media_stream_;
     const scoped_refptr<base::SingleThreadTaskRunner> main_thread_;
-    const scoped_refptr<webrtc::MediaStreamInterface> webrtc_stream_;
-    base::ThreadChecker ctor_thread_;
+    scoped_refptr<webrtc::MediaStreamInterface> webrtc_stream_;
   };
 
   void OnChanged(scoped_ptr<RemoteAudioTrackAdapters> audio_tracks,