That however exposes a bunch of failed test, so this CL also fixed a few other things:
* FakeEncoder should trust the configured FPS value rather than guesstimating itself based on the realtime clock, so as not to completely undershoot targets in offline mode. Also, compensate for key-frame overshoots when outputting delta frames.
* FrameDropper should not assuming incoming frame rate is 0 if no frames have been seen.
* Fix a bunch of test cases that started failing because they were relying on the fake encoder undershooting.
* Fix test
BUG=7664
Review-Url: https://codereview.webrtc.org/2883963002
Cr-Commit-Position: refs/heads/master@{#18473}