TestFix: fix timeline-auto-record.html test.

It had a race between timeline.stopeed event and initializeFrontend call of our test harness.
As a result sometimes it fails to add the collected output into the reloaded page just because completeTest has been called.

BUG=344238

Review URL: https://codereview.chromium.org/277343002

git-svn-id: svn://svn.chromium.org/blink/trunk@173885 bbb929c8-8fbe-4397-9dbb-9b2b20218538