Add ThreadChecker class to ThreadUtils

Add ThreadChecker class to ThreadUtils

This class can be used for checking that method calls are made on the correct thread.

R=magjed@webrtc.org

Committed: https://crrev.com/418503275c52dba03c1c9dffec8aabfacd33421e
Cr-Commit-Position: refs/heads/master@{#10173}

[perkj_webrtc, 2015-10-05 14:14:31]

perkj@webrtc.org changed reviewers:
+ magjed@webrtc.org

[perkj_webrtc, 2015-10-05 14:14:31]

please?

[magjed_webrtc, 2015-10-05 14:31:23]

lgtm! I look forward to using this.

[perkj_webrtc, 2015-10-05 14:46:29]

The CQ bit was checked by perkj@webrtc.org

[commit-bot: I haz the power, 2015-10-05 14:46:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1384303002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1384303002/1

[commit-bot: I haz the power, 2015-10-05 16:46:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-05 16:47:00]

Try jobs failed on following builders:
  android_arm64_rel on tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  android_dbg on tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  android_rel on tryserver.webrtc (JOB_TIMED_OUT, no build URL)

[perkj_webrtc, 2015-10-05 18:49:23]

Committed patchset #1 (id:1) manually as
418503275c52dba03c1c9dffec8aabfacd33421e (presubmit successful).

[commit-bot: I haz the power, 2015-10-05 18:49:26]

Patchset 1 (id:??) landed as
https://crrev.com/418503275c52dba03c1c9dffec8aabfacd33421e
Cr-Commit-Position: refs/heads/master@{#10173}