Support alpha channel recording for VPX in MediaRecorder

media/muxers/webm_muxer.h

Index: media/muxers/webm_muxer.h
diff --git a/media/muxers/webm_muxer.h b/media/muxers/webm_muxer.h
index e8ac3a4a855b38d501fd59e438d5eda01d23b9c4..3e371a6747da83da0933ec37bf73e21ae35c3c80 100644
--- a/media/muxers/webm_muxer.h
+++ b/media/muxers/webm_muxer.h
@@ -69,6 +69,7 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
   // to WebM Segment. Either one returns true on success.

[mcasas, 2017/03/08 22:38:48]

Say what |encoded_alpha_data| is and that it
can perfectly be nullptr.

[emircan, 2017/03/09 01:45:41]

Done.

   bool OnEncodedVideo(const VideoParameters& params,
                       std::unique_ptr<std::string> encoded_data,
+                      std::unique_ptr<std::string> encoded_alpha_data,
                       base::TimeTicks timestamp,
                       bool is_key_frame);
   bool OnEncodedAudio(const media::AudioParameters& params,
@@ -101,6 +102,7 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
 
   // Helper to simplify saving frames. Returns true on success.
   bool AddFrame(std::unique_ptr<std::string> encoded_data,
+                std::unique_ptr<std::string> encoded_alpha_data,
                 uint8_t track_index,
                 base::TimeDelta timestamp,
                 bool is_key_frame);
@@ -145,11 +147,13 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
   // received, if expected, since WebM headers can only be written once.
   struct EncodedVideoFrame {
     EncodedVideoFrame(std::unique_ptr<std::string> data,
+                      std::unique_ptr<std::string> alpha_data,
                       base::TimeTicks timestamp,
                       bool is_keyframe);
     ~EncodedVideoFrame();
 
     std::unique_ptr<std::string> data;
+    std::unique_ptr<std::string> alpha_data;
     base::TimeTicks timestamp;
     bool is_keyframe;