Allow setting thread priorities in Chromium on all but linux platforms.
The previous check was overly broad, so narrowing it down to linux only.

R=pbos@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/43929004

Cr-Original-Commit-Position: refs/heads/master@{#8837}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a3ffc56cee936aada92a822ea8a973fc43ad951d
1 file changed