Add GUARDED_BY's in FlexfecReceiver.

Add GUARDED_BY's in FlexfecReceiver.

BUG=webrtc:5654
Review-Url: https://codereview.webrtc.org/2589583004
Cr-Commit-Position: refs/heads/master@{#15688}
Committed: https://chromium.googlesource.com/external/webrtc/+/8b5c345ee55e390c7e78241e5924c6674dc5aa3f

[brandtr, 2016-12-19 16:15:34]

brandtr@webrtc.org changed reviewers:
+ danilchap@webrtc.org

[danilchap, 2016-12-19 16:39:29]

lgtm

[brandtr, 2016-12-19 16:40:03]

The CQ bit was checked by brandtr@webrtc.org

[commit-bot: I haz the power, 2016-12-19 16:40:06]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-12-19 18:02:30]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1482165603132950, "parent_rev":
"bb7066f9662a638f2f3b2f6100880ca595da0c3c", "commit_rev":
"8b5c345ee55e390c7e78241e5924c6674dc5aa3f"}

[commit-bot: I haz the power, 2016-12-19 18:02:32]

Description was changed from

==========
Add GUARDED_BY's in FlexfecReceiver.

BUG=webrtc:5654
==========

to

==========
Add GUARDED_BY's in FlexfecReceiver.

BUG=webrtc:5654

Review-Url: https://codereview.webrtc.org/2589583004
Cr-Commit-Position: refs/heads/master@{#15688}
Committed:
https://chromium.googlesource.com/external/webrtc/+/8b5c345ee55e390c7e78241e5...
==========

[commit-bot: I haz the power, 2016-12-19 18:02:33]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/8b5c345ee55e390c7e78241e5...