Turn off autofill highlight when changing option in an autofilled <select> element

R=isherman@chromium.org, tkent@chromium.org
BUG=412311

Review URL: https://codereview.chromium.org/553983012

git-svn-id: svn://svn.chromium.org/blink/trunk@182528 bbb929c8-8fbe-4397-9dbb-9b2b20218538