Fix for 2 failing text autosizing layout tests on the Mac platform.

BUG=337852
TBR=mvanouwerkerk@chromium.org

Review URL: https://codereview.chromium.org/138543006

git-svn-id: svn://svn.chromium.org/blink/trunk@166646 bbb929c8-8fbe-4397-9dbb-9b2b20218538