Don't touch the renderer without the lock!

Don't touch the renderer without the lock!

It's accessed concurrently on the render thread and the media thread internally and externally.

BUG=452093
TEST=none

Committed: https://crrev.com/3a9f3a8b726c46f9907a9b1d1658f3e0c6169377
Cr-Commit-Position: refs/heads/master@{#313158}

[DaleCurtis, 2015-01-26 19:28:35]

dalecurtis@chromium.org changed reviewers:
+ xhwang@chromium.org

[xhwang, 2015-01-26 20:57:58]

lgtm

[DaleCurtis, 2015-01-26 21:00:04]

The CQ bit was checked by dalecurtis@chromium.org

[commit-bot: I haz the power, 2015-01-26 21:01:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/879483004/1

[commit-bot: I haz the power, 2015-01-26 22:44:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-26 22:45:27]

Patchset 1 (id:??) landed as
https://crrev.com/3a9f3a8b726c46f9907a9b1d1658f3e0c6169377
Cr-Commit-Position: refs/heads/master@{#313158}