Reduce locking in overuse frame detector now that (as of r9508) the observer_ and options_ can only

Reduce locking in overuse frame detector now that (as of r9508) the observer_ and options_ can only be set at construction time. E.g. no lock is any longer held while doing the callback.

BUG=

Committed: https://crrev.com/74d85e19ae118ed1c98ac45284b2295134633220
Cr-Commit-Position: refs/heads/master@{#10043}

[åsapersson, 2015-09-23 09:30:04]

Patchset #5 (id:70001) has been deleted

[åsapersson, 2015-09-23 13:01:49]

asapersson@webrtc.org changed reviewers:
+ pbos@webrtc.org

[pbos-webrtc, 2015-09-23 13:36:56]

lgtm

[åsapersson, 2015-09-24 07:35:07]

The CQ bit was checked by asapersson@webrtc.org

[commit-bot: I haz the power, 2015-09-24 07:35:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1228853004/90001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1228853004/90001

[commit-bot: I haz the power, 2015-09-24 07:53:37]

Committed patchset #5 (id:90001)

[commit-bot: I haz the power, 2015-09-24 07:53:46]

Patchset 5 (id:??) landed as
https://crrev.com/74d85e19ae118ed1c98ac45284b2295134633220
Cr-Commit-Position: refs/heads/master@{#10043}