Unset the active flag when TextTrackCues go away

Unset the active flag when TextTrackCues go away
https://bugs.webkit.org/show_bug.cgi?id=72552

Reviewed by Maciej Stachowiak.

Source/WebCore:

Test: media/track/track-active-cues.html

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::loadTimerFired): Configure new text tracks before preparing to load
    so we know about all tracks when resource selection begins.
(WebCore::HTMLMediaElement::prepareForLoad): Call updateActiveTextTrackCues after setting
    to m_readyState is HAVE_NOTHING so all cues get deactivated. Don't build list of
    available text tracks because resource selection won't actually start until after the load timer fires.
(WebCore::HTMLMediaElement::loadInternal): Build list of non-disabled tracks.
(WebCore::HTMLMediaElement::updateActiveTextTrackCues):  Clear the active flag on all cues
    when m_readyState is HAVE_NOTHING or m_player is 0.
(WebCore::HTMLMediaElement::setReadyState): Don't update m_readyState when tracks which haven't
    loaded yet will prevent events from firing. Call updateActiveTextTrackCues to ensure that the
    first cue(s) are shown as soon as possible.
(WebCore::HTMLMediaElement::userCancelledLoad): Call updateActiveTextTrackCues when when m_readyState
    is HAVE_NOTHING so all cues get deactivated.

LayoutTests:

* media/track/track-active-cues-expected.txt: Added.
* media/track/track-active-cues.html: Added.
* track-cue-mutable-text.html: Update to not run test until track and video have
    both loaded.
* media/video-test.js:
(waitForEventsAndCall): New, call the specified function after the list of events
    has been seen.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107831 268f45cc-cd09-0410-ab3c-d52691b4dbfc