Currently some video frames metadata like rotation or ntp timestamps are copied in every encoder and decoder separately. This CL makes copying to happen at a single place for send or receive side. This will make it easier to add new metadata in the future. Also, added some missing tests. Bug: webrtc:10460 Change-Id: Ia49072c3041e75433f125a61050d2982b2bec1da Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133346 Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Johannes Kron <kron@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27719}