https://bugs.webkit.org/show_bug.cgi?id=79749

Reviewed by Levi Weintraub.

Source/WebCore:

The rendering rules for WebVTT cues are slightly different
depending on the directionality determined from the characters
of the cue text. This patch implements the preliminary step
to be able to take directionality into account.

It iterates through the cue characters and setting the CSS
directionality to the one of the first strong directional character.

Test: media/track/track-cue-rendering-rtl.html

* html/track/TextTrackCue.cpp:
(WebCore::TextTrackCueBox::applyCSSProperties): Applies the determined
direction.
(WebCore::TextTrackCue::TextTrackCue): Sets the default value for the
display direction.
(WebCore::isCueParagraphSeparator): Tests for explicit unicode characters
that are paragraph separators.
(WebCore):
(WebCore::TextTrackCue::determineTextDirection): Determined the direction
by the first strong directional character found.
(WebCore::TextTrackCue::calculateDisplayParameters): Updated.
(WebCore::TextTrackCue::getCSSWritingDirection): Return the determined CSS
writing direction.
* html/track/TextTrackCue.h:
(TextTrackCue):

LayoutTests:

* media/track/captions-webvtt/captions-rtl.vtt: Added.
* media/track/track-cue-rendering-rtl-expected.txt: Added.
* media/track/track-cue-rendering-rtl.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146128 268f45cc-cd09-0410-ab3c-d52691b4dbfc