Remove -webkit-border-fit

"Intent to remove" thread:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/6DTvWsADTL8
3 LGTM's from ojan@, jochen@ and abarth@.

Review URL: https://codereview.chromium.org/607593002

git-svn-id: svn://svn.chromium.org/blink/trunk@183072 bbb929c8-8fbe-4397-9dbb-9b2b20218538