[webrtc-pc] new commits pushed by taylor-b

The following commits were just pushed by taylor-b to https://github.com/w3c/webrtc-pc:

* Ensure that "track" events fire before the SRD promise resolves. (#1519)

* Ensure that "track" events fire before the SRD promise resolves.

Fixes #1508.

This was the behavior before, but I accidentally broke it in PR #1136.

This ensures that if, for example, a description is applied with
audio/video tracks in the same stream, the order of events is:

1. "track" event with audio track, and stream that contains both tracks.
2. "track" event with video track, and stream that contains both tracks.
3. SRD promise resolves.

* Put enums in <code> blocks.

* Don't queue a task to update the muted state.

* Add missing quotes and <code> tag
  by Taylor Brandstetter
https://github.com/w3c/webrtc-pc/commit/20e34458c7d13dc50405a879b52811ca5c3c5d8f