https://bugs.webkit.org/show_bug.cgi?id=106199

Reviewed by Eric Carlson.

Source/WebCore:

The browser is crashing if a text track is added through JavaScript,
due to the fact that the containing block is not marked as inline at
the time RenderTextTrackCue::layout() is called. The fix consists
of ensuring that the pseudo id is set, even if the track isn't
yet visible.

Test: media/track/track-cue-inline-assertion-crash.html

* html/track/TextTrackCue.cpp:
(WebCore::TextTrackCue::updateDisplayTree): The pseudo-id should
be set when the display tree is generated.
(WebCore::TextTrackCue::getDisplayTree): Added extra check to not
do unneccessary logic if the track will never be displayed.

LayoutTests:

* media/track/track-cue-inline-assertion-crash-expected.txt: Added.
* media/track/track-cue-inline-assertion-crash.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138966 268f45cc-cd09-0410-ab3c-d52691b4dbfc