[EXPERIMENTAL] Generic stereo codec with index header sending single frames

api/video/video_frame_buffer.h

Index: api/video/video_frame_buffer.h
diff --git a/api/video/video_frame_buffer.h b/api/video/video_frame_buffer.h
index c8d02a153f5f9ae7cafc3959a0b39b85b2cbd5d1..a63be92200ac5fe8562059321c450ea507ee2086 100644
--- a/api/video/video_frame_buffer.h
+++ b/api/video/video_frame_buffer.h
@@ -97,11 +97,15 @@ class PlanarYuvBuffer : public VideoFrameBuffer {
 
 class I420BufferInterface : public PlanarYuvBuffer {
  public:
-  Type type() const final;
+  Type type() const override;
 
   int ChromaWidth() const final;
   int ChromaHeight() const final;
 
+  bool HasAlpha() const;
+  virtual const uint8_t* DataA() const;
+  virtual int StrideA() const;
+
   rtc::scoped_refptr<I420BufferInterface> ToI420() final;
 
  protected: