Fix deadlock in WebRtcMediaStreamTrackAdapterMap.

Fix deadlock in WebRtcMediaStreamTrackAdapterMap.

BUG=736725
Review-Url: https://codereview.chromium.org/2958723003
Cr-Commit-Position: refs/heads/master@{#482241}
Committed: https://chromium.googlesource.com/chromium/src/+/2d67a5f9f90cb31b4358c74e1450f4bc83c7293e

[hbos_chromium, 2017-06-26 10:15:57]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-26 10:16:10]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[hbos_chromium, 2017-06-26 10:16:13]

hbos@chromium.org changed reviewers:
+ guidou@chromium.org

[hbos_chromium, 2017-06-26 10:16:13]

Please take a look, guidou.

[Guido Urdaneta, 2017-06-26 10:20:12]

lgtm

[Guido Urdaneta, 2017-06-26 10:20:13]

lgtm

[hbos_chromium, 2017-06-26 10:47:19]

The CQ bit was unchecked by hbos@chromium.org

[hbos_chromium, 2017-06-26 10:47:24]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2017-06-26 10:47:37]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-26 11:30:25]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1498474044247110, "parent_rev":
"1c2df6fd6cb908bb003302ceaa8b1e795c54a6e3", "commit_rev":
"2d67a5f9f90cb31b4358c74e1450f4bc83c7293e"}

[commit-bot: I haz the power, 2017-06-26 11:30:39]

Description was changed from

==========
Fix deadlock in WebRtcMediaStreamTrackAdapterMap.

BUG=736725
==========

to

==========
Fix deadlock in WebRtcMediaStreamTrackAdapterMap.

BUG=736725

Review-Url: https://codereview.chromium.org/2958723003
Cr-Commit-Position: refs/heads/master@{#482241}
Committed:
https://chromium.googlesource.com/chromium/src/+/2d67a5f9f90cb31b4358c74e1450...
==========

[commit-bot: I haz the power, 2017-06-26 11:30:40]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/2d67a5f9f90cb31b4358c74e1450...