tracing: update docs
tracing: update docs

centricular/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,centricular/gstreamer,centricular/gstreamer,centricular/gstreamer,centricular/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer