Enable ExtensionApiTest.MessagingUserGesture test

Enable ExtensionApiTest.MessagingUserGesture test

This test was disabled temporarily while changing how the fake
UserGestureIndicator is set for tests.

Depends on blink patch:
https://codereview.chromium.org/518633002/

BUG=408426, 406336
NOTRY=true
TBR=jochen@chromium.org

Committed: https://crrev.com/9e55d685552542d6d6e323f778369367311277c0
Cr-Commit-Position: refs/heads/master@{#294076}

[Zeeshan Qureshi, 2014-09-10 01:57:34]

zeeshanq@chromium.org changed reviewers:
- jochen@chromium.org

[Zeeshan Qureshi, 2014-09-10 01:57:35]

Already reviewed and trybots run in https://codereview.chromium.org/521743002/

[Zeeshan Qureshi, 2014-09-10 01:58:01]

The CQ bit was checked by zeeshanq@chromium.org

[commit-bot: I haz the power, 2014-09-10 02:00:02]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/zeeshanq@chromium.org/557153002/1

[Zeeshan Qureshi, 2014-09-10 02:06:44]

The CQ bit was unchecked by zeeshanq@chromium.org

[commit-bot: I haz the power, 2014-09-10 02:06:48]

Committed patchset #1 (id:1) as 40a115b034b6e9534f8b38c5ab59b7526c5745df

[Zeeshan Qureshi, 2014-09-10 02:13:23]

zeeshanq@chromium.org changed reviewers:
+ jochen@chromium.org

[commit-bot: I haz the power, 2014-09-10 03:57:44]

Patchset 1 (id:??) landed as
https://crrev.com/9e55d685552542d6d6e323f778369367311277c0
Cr-Commit-Position: refs/heads/master@{#294076}