dbe2b8744f
This will allow a sender to stop/start sending media on the application's demand. Among other things, this can allow an application to set a track on a sender while the encoding(s) are inactive, allowing the encoder to be initialized for that track, then later set the encodings to "active" to instantly start sending the track. Review URL: https://codereview.webrtc.org/1822923002 Cr-Commit-Position: refs/heads/master@{#12094}