GitLab

This is a once callback because it is run to indicate the completion of
the RequestEncodedFrame method:
* https://cs.chromium.org/chromium/src/media/cast/cast_receiver.h?rcl=dbfabe22380e821376c625ccabce8cc92e1c4b2b&l=43
* https://cs.chromium.org/chromium/src/media/cast/receiver/frame_receiver.h?rcl=dbfabe22380e821376c625ccabce8cc92e1c4b2b&l=62

This callback is placed in a queue by RequestEncodedFrame in:
* https://cs.chromium.org/chromium/src/media/cast/receiver/frame_receiver.cc?rcl=dbfabe22380e821376c625ccabce8cc92e1c4b2b&l=80

And it is extracted from the queue in:
* https://cs.chromium.org/chromium/src/media/cast/receiver/frame_receiver.cc?rcl=dbfabe22380e821376c625ccabce8cc92e1c4b2b&l=281

And passed to EmitOneFrame to be executed once in:
* https://cs.chromium.org/chromium/src/media/cast/receiver/frame_receiver.cc?rcl=dbfabe22380e821376c625ccabce8cc92e1c4b2b&l=301

This is part of the base::Callback migration.

Context: https://cs.chromium.org/chromium/src/docs/callback.md?rcl=9fcc3764aea8f97e9f6de4a9ee61d554e67edcda&l=40

Bug: 714018
Change-Id: Iaaaa1b830c5f8e65a94124233d28614e36c8f1de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2077994
Commit-Queue: Jose Lopes <jabolopes@google.com>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Albert J. Wong <ajwong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747613}