Fix expectation for fast/sub-pixel/ellipsis-zoom.html.

TBR=cbiesinger@chromium.org

Review URL: https://codereview.chromium.org/21677002

git-svn-id: svn://svn.chromium.org/blink/trunk@155371 bbb929c8-8fbe-4397-9dbb-9b2b20218538