Gardening. width-using-ems.html no longer crashes as of r158797

NOTRY=true
TBR=steveblock

Review URL: https://codereview.chromium.org/26438002

git-svn-id: svn://svn.chromium.org/blink/trunk@159094 bbb929c8-8fbe-4397-9dbb-9b2b20218538