Re-add a thread check in Call::Call that was removed by mistake in a rebase.

Re-add a thread check in Call::Call that was removed by mistake in a rebase.

BUG=

Committed: https://crrev.com/56a34df92807d95a2660765be10abef7c779666f
Cr-Commit-Position: refs/heads/master@{#10623}

[the sun, 2015-11-12 10:52:51]

solenberg@webrtc.org changed reviewers:
+ mflodman@webrtc.org

[mflodman, 2015-11-12 13:39:07]

lgtm

[the sun, 2015-11-12 13:41:59]

The CQ bit was checked by solenberg@webrtc.org

[the sun, 2015-11-12 13:42:00]

The patchset sent to the CQ was uploaded after l-g-t-m from mflodman@webrtc.org
Link to the patchset: https://codereview.webrtc.org/1434263002/#ps20001 (title:
"rebase")

[commit-bot: I haz the power, 2015-11-12 13:42:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1434263002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1434263002/20001

[commit-bot: I haz the power, 2015-11-12 15:42:29]

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

[commit-bot: I haz the power, 2015-11-12 15:42:29]

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

[the sun, 2015-11-12 15:59:50]

The CQ bit was checked by solenberg@webrtc.org

[commit-bot: I haz the power, 2015-11-12 16:00:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1434263002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1434263002/20001

[commit-bot: I haz the power, 2015-11-12 16:24:46]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-12 16:25:03]

Patchset 2 (id:??) landed as
https://crrev.com/56a34df92807d95a2660765be10abef7c779666f
Cr-Commit-Position: refs/heads/master@{#10623}