Remove unneeded includes from trace_posix.cc.
Remove unneeded includes from trace_posix.cc.

TESTED=trybots
R=niklas.enbom@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/3629004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5973f3a24a91d2d0ae7b982fcabdcdb5c58a9263

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc