GitLab

Add CastExternalBeginFrameClient to eventually allow 4hz refresh rate on
audio-only cast devices

Bug: b/139299756
Test: Compile and run cast_shell
Change-Id: Ia2e1531a1035ed92ee61cee69dc24c491d6ca109
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1763435
Commit-Queue: Shawn Gallea <sagallea@google.com>
Reviewed-by: Michael Spang <spang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690098}