1 files changed, 35 insertions, 1 deletions
diff --git a/media/base/video_source_base.h b/media/base/video_source_base.h
index 59b7dab164..2644723aa7 100644
--- a/media/base/video_source_base.h
+++ b/media/base/video_source_base.h
@@ -17,10 +17,14 @@
 #include "api/video/video_frame.h"
 #include "api/video/video_sink_interface.h"
 #include "api/video/video_source_interface.h"
+#include "rtc_base/system/no_unique_address.h"
 
 namespace rtc {
 
-// VideoSourceBase is not thread safe.
+// VideoSourceBase is not thread safe. Before using this class, consider using
+// VideoSourceBaseGuarded below instead, which is an identical implementation
+// but applies a sequence checker to help protect internal state.
+// TODO(bugs.webrtc.org/12780): Delete this class.
 class VideoSourceBase : public VideoSourceInterface<webrtc::VideoFrame> {
  public:
   VideoSourceBase();
@@ -44,6 +48,36 @@ class VideoSourceBase : public VideoSourceInterface<webrtc::VideoFrame> {
   std::vector<SinkPair> sinks_;
 };
 
+// VideoSourceBaseGuarded assumes that operations related to sinks, occur on the
+// same TQ/thread that the object was constructed on.
+class VideoSourceBaseGuarded : public VideoSourceInterface<webrtc::VideoFrame> {
+ public:
+  VideoSourceBaseGuarded();
+  ~VideoSourceBaseGuarded() override;
+
+  void AddOrUpdateSink(VideoSinkInterface<webrtc::VideoFrame>* sink,
+                       const VideoSinkWants& wants) override;
+  void RemoveSink(VideoSinkInterface<webrtc::VideoFrame>* sink) override;
+
+ protected:
+  struct SinkPair {
+    SinkPair(VideoSinkInterface<webrtc::VideoFrame>* sink, VideoSinkWants wants)
+        : sink(sink), wants(wants) {}
+    VideoSinkInterface<webrtc::VideoFrame>* sink;
+    VideoSinkWants wants;
+  };
+
+  SinkPair* FindSinkPair(const VideoSinkInterface<webrtc::VideoFrame>* sink);
+  const std::vector<SinkPair>& sink_pairs() const;
+
+  // Keep the `source_sequence_` checker protected to allow sub classes the
+  // ability to call Detach() if/when appropriate.
+  RTC_NO_UNIQUE_ADDRESS webrtc::SequenceChecker source_sequence_;
+
+ private:
+  std::vector<SinkPair> sinks_ RTC_GUARDED_BY(&source_sequence_);
+};
+
 }  // namespace rtc
 
 #endif  // MEDIA_BASE_VIDEO_SOURCE_BASE_H_