Remove TreatNullAs=NullString for media interfaces

Remove TreatNullAs=NullString for media interfaces

The spec doesn't have special null handling here:
http://www.whatwg.org/specs/web-apps/current-work/multipage/the-video-element.html

The updated test was run in Firefox Nightly (with media.webvtt.enabled),
IE11 Release Preview and Opera 12.16 (Presto 2.12.388). Everything
passes, with these exceptions:

No other browser supports the mediaGroup property.

The preload default value is "metadata" in IE11 and Presto, and "" in
Firefox. The spec suggests "metadata". Bugs filed:
https://code.google.com/p/chromium/issues/detail?id=310450
https://bugzilla.mozilla.org/show_bug.cgi?id=929890

BUG=310298
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=160318

[philipj_slow, 2013-10-22 21:54:59]

Erik said in <http://code.google.com/p/chromium/issues/detail?id=304959#c9> that
he'd rather have a mass removal, but I already had this lined up...

If someone wants to do the mass removal soon, you can take over this review and
do the rest :)

[arv (Not doing code reviews), 2013-10-22 22:01:23]

LGTM

[haraken, 2013-10-22 22:47:05]

LGTM, given the spec and the behavior of Firefox and IE. Needs an approval from
an API owner.

[Inactive, 2013-10-22 23:17:25]

On 2013/10/22 21:54:59, philipj wrote:
> Erik said in <http://code.google.com/p/chromium/issues/detail?id=304959#c9>
that
> he'd rather have a mass removal, but I already had this lined up...
> 
> If someone wants to do the mass removal soon, you can take over this review
and
> do the rest :)

If mass removal is done, it should be done very carefully because the extended
attribute should be kept for some reflected attributes, as per their respective
specs.

[Inactive, 2013-10-22 23:26:03]

Lgtm but I think the cl description is a bit light. Optimally, it should explain
the behavior of other browsers and contain a link to the spec.

This change needs approval from an api owner.

[philipj_slow, 2013-10-23 06:18:16]

On 2013/10/22 23:17:25, Chris Dumez wrote:
> On 2013/10/22 21:54:59, philipj wrote:
> > Erik said in <http://code.google.com/p/chromium/issues/detail?id=304959#c9>
> that
> > he'd rather have a mass removal, but I already had this lined up...
> > 
> > If someone wants to do the mass removal soon, you can take over this review
> and
> > do the rest :)
> 
> If mass removal is done, it should be done very carefully because the extended
> attribute should be kept for some reflected attributes, as per their
respective
> specs.

Indeed, so I won't volunteer to do a mass removal, but clearly did volunteer to
do a little bit :)

[jochen (gone - plz use gerrit), 2013-10-23 07:01:26]

lgtm

[commit-bot: I haz the power, 2013-10-23 07:03:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/philipj@opera.com/35803004/1

[commit-bot: I haz the power, 2013-10-23 08:24:13]

Change committed as 160318