Restoring behavior where PeerConnection tracks changes to MediaStreams.

talk/app/webrtc/mediastreamobserver.cc

 /*
  * libjingle
  * Copyright 2015 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
  *     this list of conditions and the following disclaimer in the documentation
  *     and/or other materials provided with the distribution.
  *  3. The name of the author may not be used to endorse or promote products
  *     derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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  */
 
 #include "talk/app/webrtc/mediastreamobserver.h"
 
-// This file is currently stubbed so that Chromium's build files can be updated.
+#include <algorithm>
+
+namespace webrtc {
+
+MediaStreamObserver::MediaStreamObserver(MediaStreamInterface* stream)
+    : stream_(stream),
+      cached_audio_tracks_(stream->GetAudioTracks()),
+      cached_video_tracks_(stream->GetVideoTracks()) {
+  stream_->RegisterObserver(this);
+}
+
+MediaStreamObserver::~MediaStreamObserver() {
+  stream_->UnregisterObserver(this);
+}
+
+void MediaStreamObserver::OnChanged() {
+  AudioTrackVector new_audio_tracks = stream_->GetAudioTracks();
+  VideoTrackVector new_video_tracks = stream_->GetVideoTracks();
+
+  // Find removed audio tracks.
+  for (const auto& cached_track : cached_audio_tracks_) {
+    auto it = std::find_if(
+        new_audio_tracks.begin(), new_audio_tracks.end(),
+        [cached_track](const AudioTrackVector::value_type& new_track) {
+          return new_track->id().compare(cached_track->id()) == 0;
+        });
+    if (it == new_audio_tracks.end()) {
+      SignalAudioTrackRemoved(cached_track.get(), stream_);
+    }
+  }
+
+  // Find added audio tracks.
+  for (const auto& new_track : new_audio_tracks) {
+    auto it = std::find_if(
+        cached_audio_tracks_.begin(), cached_audio_tracks_.end(),
+        [new_track](const AudioTrackVector::value_type& cached_track) {
+          return new_track->id().compare(cached_track->id()) == 0;
+        });
+    if (it == cached_audio_tracks_.end()) {
+      SignalAudioTrackAdded(new_track.get(), stream_);
+    }
+  }
+
+  // Find removed video tracks.
+  for (const auto& cached_track : cached_video_tracks_) {
+    auto it = std::find_if(
+        new_video_tracks.begin(), new_video_tracks.end(),
+        [cached_track](const VideoTrackVector::value_type& new_track) {
+          return new_track->id().compare(cached_track->id()) == 0;
+        });
+    if (it == new_video_tracks.end()) {
+      SignalVideoTrackRemoved(cached_track.get(), stream_);
+    }
+  }
+
+  // Find added video tracks.
+  for (const auto& new_track : new_video_tracks) {
+    auto it = std::find_if(
+        cached_video_tracks_.begin(), cached_video_tracks_.end(),
+        [new_track](const VideoTrackVector::value_type& cached_track) {
+          return new_track->id().compare(cached_track->id()) == 0;
+        });
+    if (it == cached_video_tracks_.end()) {
+      SignalVideoTrackAdded(new_track.get(), stream_);
+    }
+  }
+
+  cached_audio_tracks_ = new_audio_tracks;
+  cached_video_tracks_ = new_video_tracks;
+}
+
+}  // namespace webrtc