commit dc4f75f7eed26fff21d475ddacaba073eab3c8a0
author Henrik Boström <hbos@webrtc.org> Mon Apr 20 10:04:12 2020
committer Commit Bot <commit-bot@chromium.org> Mon Apr 20 10:54:53 2020
tree 7bbc70d639d2df0e39cd390f3e5049c28753eb70
parent 4c3a7dbe1482e389b54c799f332c8ec6e5ac6af9

[Adaptation] Make ResourceUsageState nullable, remove kStable.

This CL is part of the Call-Level Adaptation Processing design doc:
https://docs.google.com/document/d/1ZyC26yOCknrrcYa839ZWLxD6o6Gig5A3lVTh4E41074/edit?usp=sharing

The ResourceUsageState was written as: {kOveruse, kStable, kUnderuse}.
The assumption was that if a resource neither wanted to adapt up or
down it would report kStable. But with the addition of
Resource::IsAdaptationUpAllowed() (prior CL) the notion of being
"stable" was already captured outside of ResourceUsageState.
Furthermore, kStable failed to capture what IsAdaptationUpAllowed() did
not: whether we can go up depends on the resulting resolution or frame
rate (restrictions_after). Perhaps we can go up a little, but not a lot.

This CL also adds Resource::ClearUsageState(). After applying an
adaptation, all usage states become invalidated (new measurements are
needed to know if we are still over- or underusing). This was always
the case, but prior to this CL this was not accurately reflected in the
Resource::usage_state() in-between measurements.

Bug: webrtc:11172
Change-Id: I140ff3114025b7732e530564690783e168d2509b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173088
Reviewed-by: Evan Shrubsole <eshr@google.com>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31110}