Check if Fragment is attached in onClick

Check if Fragment is attached in onClick

We still don't have sensible explanation, but the current theory
is that the Fragment-related transaction creates a race wrt
onClick and Detach.

BUG=467846
Committed: https://crrev.com/0d4c89148c0f10a518805aea0d8c6c70bd490900
Cr-Commit-Position: refs/heads/master@{#323846}

[aruslan, 2015-04-03 15:54:46]

aruslan@chromium.org changed reviewers:
+ dtrainor@chromium.org

[aruslan, 2015-04-03 15:54:46]

PTAL, thanks!

[David Trainor- moved to gerrit, 2015-04-03 23:03:29]

lgtm

[aruslan, 2015-04-03 23:03:35]

The CQ bit was checked by aruslan@chromium.org

[commit-bot: I haz the power, 2015-04-03 23:04:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1055663003/1

[commit-bot: I haz the power, 2015-04-03 23:29:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-03 23:30:01]

Patchset 1 (id:??) landed as
https://crrev.com/0d4c89148c0f10a518805aea0d8c6c70bd490900
Cr-Commit-Position: refs/heads/master@{#323846}