Mark transformed-focused-text-input as flaky mac image

TBR=alancutter@chromium.org
NOTRY=true
BUG=399430

Review URL: https://codereview.chromium.org/432123002

git-svn-id: svn://svn.chromium.org/blink/trunk@179344 bbb929c8-8fbe-4397-9dbb-9b2b20218538