1 files changed, 98 insertions, 0 deletions
diff --git a/third_party/libwebrtc/pc/media_stream_observer.cc b/third_party/libwebrtc/pc/media_stream_observer.cc
new file mode 100644
index 0000000000..6264a7657a
--- /dev/null
+++ b/third_party/libwebrtc/pc/media_stream_observer.cc
@@ -0,0 +1,98 @@
+/*
+ *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "pc/media_stream_observer.h"
+
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+
+namespace webrtc {
+
+MediaStreamObserver::MediaStreamObserver(
+    MediaStreamInterface* stream,
+    std::function<void(AudioTrackInterface*, MediaStreamInterface*)>
+        audio_track_added_callback,
+    std::function<void(AudioTrackInterface*, MediaStreamInterface*)>
+        audio_track_removed_callback,
+    std::function<void(VideoTrackInterface*, MediaStreamInterface*)>
+        video_track_added_callback,
+    std::function<void(VideoTrackInterface*, MediaStreamInterface*)>
+        video_track_removed_callback)
+    : stream_(stream),
+      cached_audio_tracks_(stream->GetAudioTracks()),
+      cached_video_tracks_(stream->GetVideoTracks()),
+      audio_track_added_callback_(std::move(audio_track_added_callback)),
+      audio_track_removed_callback_(std::move(audio_track_removed_callback)),
+      video_track_added_callback_(std::move(video_track_added_callback)),
+      video_track_removed_callback_(std::move(video_track_removed_callback)) {
+  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_) {
+    if (absl::c_none_of(
+            new_audio_tracks,
+            [cached_track](const AudioTrackVector::value_type& new_track) {
+              return new_track->id() == cached_track->id();
+            })) {
+      audio_track_removed_callback_(cached_track.get(), stream_.get());
+    }
+  }
+
+  // Find added audio tracks.
+  for (const auto& new_track : new_audio_tracks) {
+    if (absl::c_none_of(
+            cached_audio_tracks_,
+            [new_track](const AudioTrackVector::value_type& cached_track) {
+              return new_track->id() == cached_track->id();
+            })) {
+      audio_track_added_callback_(new_track.get(), stream_.get());
+    }
+  }
+
+  // Find removed video tracks.
+  for (const auto& cached_track : cached_video_tracks_) {
+    if (absl::c_none_of(
+            new_video_tracks,
+            [cached_track](const VideoTrackVector::value_type& new_track) {
+              return new_track->id() == cached_track->id();
+            })) {
+      video_track_removed_callback_(cached_track.get(), stream_.get());
+    }
+  }
+
+  // Find added video tracks.
+  for (const auto& new_track : new_video_tracks) {
+    if (absl::c_none_of(
+            cached_video_tracks_,
+            [new_track](const VideoTrackVector::value_type& cached_track) {
+              return new_track->id() == cached_track->id();
+            })) {
+      video_track_added_callback_(new_track.get(), stream_.get());
+    }
+  }
+
+  cached_audio_tracks_ = new_audio_tracks;
+  cached_video_tracks_ = new_video_tracks;
+}
+
+}  // namespace webrtc