Add content type information to encoded images and corresponding rtp extension header

webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm

Index: webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm b/webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm
index e50b225f2d3f44dbf62ad9e79e418f761a00475b..603c7a3bf68322f5c210b6390f44aca378d2a7f7 100644
--- a/webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm
+++ b/webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.mm
@@ -364,6 +364,7 @@ int H264VideoToolboxEncoder::InitEncode(const VideoCodec* codec_settings,
 
   width_ = codec_settings->width;
   height_ = codec_settings->height;
+  mode_ = codec_settings->mode;
   // We can only set average bitrate on the HW encoder.
   target_bitrate_bps_ = codec_settings->startBitrate;
   bitrate_adjuster_.SetTargetBitrateBps(target_bitrate_bps_);
@@ -722,6 +723,11 @@ void H264VideoToolboxEncoder::OnEncodedFrame(
   frame._timeStamp = timestamp;
   frame.rotation_ = rotation;
 
+  if (mode_ == kScreensharing)
+    frame.content_type_ = VideoContentType::kScreenshare;
+  else
+    frame.content_type_ = VideoContentType::kUnspecified;
+
   h264_bitstream_parser_.ParseBitstream(buffer->data(), buffer->size());
   h264_bitstream_parser_.GetLastSliceQp(&frame.qp_);