Remove inaccurate comment and expectation.

This test is a reftest and fails reliably.
TBR=pdr@chromium.org

NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/19672014

git-svn-id: svn://svn.chromium.org/blink/trunk@154599 bbb929c8-8fbe-4397-9dbb-9b2b20218538