Simplify LoadableTextTrack construction

Simplify LoadableTextTrack construction

HTMLTrackElement::parseAttribute() already sets kind, label and
language when the corresponding attributes change, so we can create a
TextTrack with the default values, leaving all of the logic for
parsing kind in TextTrack::setKind().

This leaves HTMLTrackElement::srclang() and label() unused, so just
use [Reflect] in the IDL for these attributes.

BUG=315510
TEST=media/track/opera/interfaces/TextTrack/kind.html,
     media/track/opera/interfaces/TextTrack/label.html,
     media/track/opera/interfaces/TextTrack/language.html,
     media/track/track-kind.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=161457

[jochen (gone - plz use gerrit), 2013-11-06 10:54:04]

which test covers this?

[philipj_slow, 2013-11-06 11:41:28]

On 2013/11/06 10:54:04, jochen wrote:
> which test covers this?

media/track/opera/interfaces/TextTrack/label.html
media/track/opera/interfaces/TextTrack/language.html
media/track/track-kind.html

All of these test with a HTMLTrackElement (not just TextTrack) and fail if
HTMLTrackElement::parseAttribute doesn't forward to track().

[jochen (gone - plz use gerrit), 2013-11-06 11:48:26]

cool, lgtm

[commit-bot: I haz the power, 2013-11-06 11:51:03]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/philipj@opera.com/60423008/1

[commit-bot: I haz the power, 2013-11-06 13:20:33]

Retried try job too often on win_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[commit-bot: I haz the power, 2013-11-06 13:32:45]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/philipj@opera.com/60423008/1

[commit-bot: I haz the power, 2013-11-06 14:40:16]

Change committed as 161457