Reason for revert:
Reverting this change since it didn't affect the perf regressions we were seeing and actually seems to have caused more regressions as per comment in the bug.
Original issue's description:
> Use sched_yield on all POSIX platforms in PlatformThread.
> (not only MacOS)
>
> This is a test to see if perf regressions we're seeing may be related to the use of nanosleep().
>
> BUG=695438
> TBR=solenberg@webrtc.org
>
> Review-Url: https://codereview.webrtc.org/2716683002 .
> Cr-Commit-Position: refs/heads/master@{#16807}
> Committed: 384498abb5
TBR=solenberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=695438
Review-Url: https://codereview.webrtc.org/2712133003
Cr-Commit-Position: refs/heads/master@{#16833}
Name: WebRTC URL: http://www.webrtc.org Version: 90 License: BSD License File: LICENSE Description: WebRTC provides real time voice and video processing functionality to enable the implementation of PeerConnection/MediaStream. Third party code used in this project is described in the file LICENSE_THIRD_PARTY.