Queue the cuechange event on HTMLTrackElement for proper sorting.

Queue the cuechange event on HTMLTrackElement for proper sorting.
https://bugs.webkit.org/show_bug.cgi?id=83858

Reviewed by Eric Carlson.

Source/WebCore:

No new tests. Updates to media/track/track-cues-cuechange.html and
media/track/track-mode.html

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::updateActiveTextTrackCues):
    Add HTMLTrackElement's cuechange event to the event queue rather than
    firing it synchronously.
* html/track/LoadableTextTrack.cpp:
    Remove fireCueChangeEvent() as it is no longer used.
* html/track/LoadableTextTrack.h:
    Ditto.
* html/track/TextTrack.h:
(TextTrack):
    Ditto.

LayoutTests:

* media/track/captions-webvtt/captions-fast.vtt:
    Captions were a wee bit too fast: they need to be at least 250ms apart
    for accurate testing as timeupdate events are only fired every 250ms.

* media/track/track-cues-cuechange-expected.txt:
    Changes the order that cuechange events are fired.
* media/track/track-cues-cuechange.html:
    Ditto.

* media/track/track-mode-expected.txt:
    cuechange events are now fired at the proper times.
    Test now checks for all cuechange events (both enter and exit of cues).
* media/track/track-mode.html:
    Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114171 268f45cc-cd09-0410-ab3c-d52691b4dbfc