Piggybacking simulcast id and ALR experiment id into video content type extension.

webrtc/video/rtp_video_stream_receiver.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 529 matching lines @@
   if (!rtp_payload_registry_.GetPayloadSpecifics(last_media_payload_type,
                                                  &payload_specific)) {
     LOG(LS_WARNING) << "Failed to get payload specifics.";
     return;
   }
   rtp_header.type.Video.codec = payload_specific.Video.videoCodecType;
   rtp_header.type.Video.rotation = kVideoRotation_0;
   if (header.extension.hasVideoRotation) {
     rtp_header.type.Video.rotation = header.extension.videoRotation;
   }
-  rtp_header.type.Video.content_type = VideoContentType::UNSPECIFIED;
+  rtp_header.type.Video.content_type = VideoContentType::Unspecified();
   if (header.extension.hasVideoContentType) {
     rtp_header.type.Video.content_type = header.extension.videoContentType;
   }
   rtp_header.type.Video.video_timing = {0u, 0u, 0u, 0u, 0u, 0u, false};
   if (header.extension.has_video_timing) {
     rtp_header.type.Video.video_timing = header.extension.video_timing;
   }
   rtp_header.type.Video.playout_delay = header.extension.playout_delay;
 
   OnReceivedPayloadData(nullptr, 0, &rtp_header);
@@ skipping 147 matching lines @@
     return;
 
   if (!sprop_decoder.DecodeSprop(sprop_base64_it->second.c_str()))
     return;
 
   tracker_.InsertSpsPpsNalus(sprop_decoder.sps_nalu(),
                              sprop_decoder.pps_nalu());
 }
 
 }  // namespace webrtc