We don't need a lock for the output queue on the main thread

We don't need a lock for the output queue on the main thread

The output queue is supposed to be a lock-free anyways, we're just
temporarily abusing it by having multiple producers. For those, we need
the lock when enqueuing jobs.

BUG=none
R=yangguo@chromium.org
LOG=n

Committed: https://crrev.com/09e0f6e21f2ba68fa6ed80702ca73b1808a6c782
Cr-Commit-Position: refs/heads/master@{#26824}

[Yang, 2015-02-24 13:21:07]

On 2015/02/24 13:16:13, jochen (slow) wrote:

lgtm.

[jochen (gone - plz use gerrit), 2015-02-24 13:21:27]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-02-24 13:21:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/953883002/1

[commit-bot: I haz the power, 2015-02-24 13:42:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-24 13:42:26]

Patchset 1 (id:??) landed as
https://crrev.com/09e0f6e21f2ba68fa6ed80702ca73b1808a6c782
Cr-Commit-Position: refs/heads/master@{#26824}