commit d2a1f09b1836e7192020e7987c10d7044526af81
author Henrik Boström <hbos@webrtc.org> Tue Feb 25 08:46:36 2020
committer Commit Bot <commit-bot@chromium.org> Tue Feb 25 13:17:11 2020
tree c114265d3262335adb242e0d6280805b3aa5cc86
parent 8a5776a0f8bd73e45fadf9de0beff0050e083e81

[Overuse] Make Most Adaptation Preconditions Explicit

Today OnResourceOveruse() and OnResourceUnderuse() implicitly checks
preconditions and if they pass calculate the next target, and if those
are usable it applies them to the VideoSourceRestrictions. These are two
big "MaybeAdapt" methods.

This CL takes us one step closer to "GetNextTarget", "CanApplyTarget?"
and "DoApplyTarget!"-logic, which will allow us to more easily evaluate
a multitude of alternative configurations and decide which one to pick
(e.g. multi-stream adaptation).

But it does not take us all the way there. In this CL we have:
- CanAdaptUp, CanAdaptDown: This covers *most* of the preconditions.
- OnResourceUnderuse, OnResourceOveruse: This aborts if CanAdapt returns
  false. If they pass, we calculate the next target and maybe-adapt it.

This is roughly outlined in document still in draft:
https://docs.google.com/document/d/1YMg-AycFZR1DS6hEav9OzJ3hqxFil09qPhlTAgQrU1g/edit?usp=sharing.

A future CL should make the target more explicit and we should know if
the target can be applied before we even try.

Bug: webrtc:11222
Change-Id: If18d9572884aa6ba2350e4670a1516da5835cc98
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168721
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@{#30605}