Disable flaky unit test WebFrameCSSCallbackTest.DisplayNone

TBR=pfeldman@chromium.org
BUG=306952
NOTRY=true

Review URL: https://codereview.chromium.org/34583008

git-svn-id: svn://svn.chromium.org/blink/trunk@160272 bbb929c8-8fbe-4397-9dbb-9b2b20218538