Sync the alert() IDL with the spec

Sync the alert() IDL with the spec

http://html5.org/r/8638
https://www.w3.org/Bugs/Public/show_bug.cgi?id=25686

This does not change the behavior of alert() or alert(undefined), it is
a pre-emptive change so that treating undefined as a missing optional
argument (per WebIDL) does not change the behavior.

BUG=335871
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174845

[philipj_slow, 2014-05-23 10:53:05]

PTAL

[Nils Barth (inactive), 2014-05-27 01:30:17]

LGTM.

For those following along at home: this change looks funny
(why not just
alert(optional DOMString message = "")
or similar?)
...but the reason is that users actually want to be able to
explicitly pass |undefined| as a value (for checking variable value) *or* omit
it (with *different* behavior),
so this actually needs an overload:
we want
alert() and alert(undefined)
to be treated differently.

Thanks for the fix!

[philipj_slow, 2014-05-27 07:44:24]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-05-27 07:44:41]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/philipj@opera.com/296853010/1

[commit-bot: I haz the power, 2014-05-27 07:57:29]

Change committed as 174845