Mark a couple of svg text tests as fialing on snowleopard debug

Since r162893 a handful of svg text tests have 1px diffrences
between debug and release, likely due to floating point handling.

BUG=324553
TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/97453002

git-svn-id: svn://svn.chromium.org/blink/trunk@162926 bbb929c8-8fbe-4397-9dbb-9b2b20218538