Move trace_event and associated files to webrtc/base.
Also starting to use TRACE_EVENT from thread.cc in webrtc/base, to track Invoke() calls.

BUG=
R=magjed@webrtc.org, tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42769004

Cr-Original-Commit-Position: refs/heads/master@{#8755}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7c64ed2e0c55d6402ef24a822b18fc9e6cc11299
13 files changed