Unreviewed fast/text/fallback-for-custom-font.html rebaseline

TBR=dcheng@chromium.org

Review URL: https://codereview.chromium.org/319813003

git-svn-id: svn://svn.chromium.org/blink/trunk@175594 bbb929c8-8fbe-4397-9dbb-9b2b20218538