Also test left to right rendering in rtl space test

Update fast/text/international/rtl-space.html to also test rendering of
left-to-right content.

BUG=343535
TBR=leviw@chromium.org

Review URL: https://codereview.chromium.org/173993002

git-svn-id: svn://svn.chromium.org/blink/trunk@167531 bbb929c8-8fbe-4397-9dbb-9b2b20218538