Added new AutoplayEnabledThroughLoad entry to the Blink.MediaElement.Autoplay histogram

Added new entry to the Blink.MediaElement.Autoplay histogram to account for cases where autoplay is reenabled on a Media element by a user-gesture triggered script

R=qinmin,adamk
BUG=432734
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185332

[oystein (OOO til 10th of July), 2014-11-13 00:49:36]

Patchset #1 (id:1) has been deleted

[DaleCurtis, 2014-11-13 02:25:19]

dalecurtis@chromium.org changed reviewers:
- dalecurtis@chromium.org

[DaleCurtis, 2014-11-13 02:25:35]

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

[DaleCurtis, 2014-11-13 02:25:35]

-myself since qinmin@ seems to have a better grasp of this state machine than I
do :)

[oystein (OOO til 10th of July), 2014-11-13 03:08:15]

oysteine@chromium.org changed reviewers:
- dalecurtis@chromium.org

[qinmin, 2014-11-13 03:14:54]

lgtm, please also update the histograms.xml for this

[adamk, 2014-11-13 21:10:24]

lgtm stamp for OWNERS

[oystein (OOO til 10th of July), 2014-11-13 22:14:18]

The CQ bit was checked by oysteine@chromium.org

[commit-bot: I haz the power, 2014-11-13 22:14:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/719413002/20001

[commit-bot: I haz the power, 2014-11-14 00:17:03]

Committed patchset #1 (id:20001) as 185332