HTMLMetaElement should not run script inside ::insertedInto

HTMLMetaElement should not run script inside ::insertedInto

To eventually remove the ChildNodesLazySnapshot we need to stop allowing
script to run inside ::insertedInto. It's also important since even with
the lazy snapshot we still keep getting security bugs down there.

This starts the process of removal by switching HTMLMetaElement to use
a post insertion callback.

R=ojan@chromium.org,abarth@chromium.org
BUG=357435
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170267

[tkent, 2014-03-28 01:44:27]

lgtm

[esprehn, 2014-03-28 01:44:44]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2014-03-28 01:45:15]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/esprehn@chromium.org/214003003/1

[commit-bot: I haz the power, 2014-03-28 02:45:30]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-28 02:45:30]

Try jobs failed on following builders:
  tryserver.blink on win_blink_rel

[esprehn, 2014-03-28 03:49:14]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2014-03-28 03:49:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/esprehn@chromium.org/214003003/1

[commit-bot: I haz the power, 2014-03-28 04:39:18]

Change committed as 170267