This uses sync groups in the receive stream configs for the conduits rather
than establishing sync through direct calls. When the streams are created
in call.cc, ConfigureSync is called, which results in SetSync being called
on the video stream which is the replacement for SetSyncChannel in branch 57
of webrtc.org.
With the current code, a video stream can only be synchronized to a single
audio stream. Using sync groups enforces a stronger constraint that only one
pair of audio and video streams can be synchronized for each sync group. The
comments in call.cc imply this is what is supported by webrtc.org, it seems
safer to also follow this constraint rather than circumvent it by calling
directly into the underlying code.
Differential Revision: https://phabricator.services.mozilla.com/D7445
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extra : rebase_source : fa8b1d301398edcedc6e488c51009b6667792f45
55840bf1dd