Rename structures to match terminology in the spec Bug: webrtc:10342 Change-Id: I1329abaca98ae7f82307451032d5ce1533e80772 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/143960 Reviewed-by: Philip Eliasson <philipel@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#28402}