CSS direction must be reset to ltr on <math> element.
<https://webkit.org/b/124121>

Patch by Frédéric Wang <fred.wang@free.fr> on 2013-11-10
Reviewed by Darin Adler.

Source/WebCore:

Test: mathml/presentation/direction.html

* css/mathml.css:
(math): set direction: ltr; on the <math> element.

LayoutTests:

* mathml/presentation/direction-expected.html: Added.
* mathml/presentation/direction.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159035 268f45cc-cd09-0410-ab3c-d52691b4dbfc