This patch creates a new class which provides the DegradationPreference
thread safe to all classes that need if (BalancedConstraint and
QpScalerResource). It also broadcasts to all listeners when the
preferences are updated, so the ResourceAdaptationProcessor can update
the video if needed.
In future work, this could be used to remove the need for two task
queues for the VideoStreamEncoder resources.
Bug: webrtc:11700
Change-Id: I05480db8b7157b5643f6f86ec9c64850839b3e76
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/177522
Commit-Queue: Evan Shrubsole <eshr@google.com>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31623}
