Reason for revert:
Less precise FrameGeneratorCapturer broke CallPerfTest.ReceivesCpuOveruseAndUnderuse on Android
Original issue's description:
> Rewrite frame generator capturer to use TaskQueue instead of EventTimeWrapper
>
> BUG=webrtc:7301
>
> Review-Url: https://codereview.webrtc.org/2740723002
> Cr-Commit-Position: refs/heads/master@{#17161}
> Committed: 7c5503a8b3TBR=kjellander@webrtc.org,sprang@webrtc.org,tommi@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:7301
Review-Url: https://codereview.webrtc.org/2739393002
Cr-Commit-Position: refs/heads/master@{#17163}