[Ozone-Drm] Do not try to take ref_ptr from destructor

[Ozone-Drm] Do not try to take ref_ptr from destructor

Can't post a task with a ref-counted instance of the watcher from the
destructor.

BUG=467170
Committed: https://crrev.com/8c08f77eae4c223b72d0a404b9139b179ec53e24
Cr-Commit-Position: refs/heads/master@{#320739}

[dnicoara, 2015-03-16 15:15:29]

dnicoara@chromium.org changed reviewers:
+ alexst@chromium.org

[dnicoara, 2015-03-16 15:15:29]

PTAL

[alexst (slow to review), 2015-03-16 15:22:13]

lgtm

[dnicoara, 2015-03-16 15:44:50]

Updated to actually wait on the WaitableEvent

[dnicoara, 2015-03-16 16:57:50]

The CQ bit was checked by dnicoara@chromium.org

[dnicoara, 2015-03-16 16:57:50]

The patchset sent to the CQ was uploaded after l-g-t-m from alexst@chromium.org
Link to the patchset: https://codereview.chromium.org/1006403002/#ps20001
(title: "Wait")

[commit-bot: I haz the power, 2015-03-16 16:58:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1006403002/20001

[commit-bot: I haz the power, 2015-03-16 17:05:14]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-16 17:05:49]

Patchset 2 (id:??) landed as
https://crrev.com/8c08f77eae4c223b72d0a404b9139b179ec53e24
Cr-Commit-Position: refs/heads/master@{#320739}