Unflaky inspector/timeline/timeline-script-tag-1.html

It was UpdateCounter event which might arrive from gpu thread.
I filtered it out because it is not the thing we test here.

BUG=384956

Review URL: https://codereview.chromium.org/358143002

git-svn-id: svn://svn.chromium.org/blink/trunk@177211 bbb929c8-8fbe-4397-9dbb-9b2b20218538