Gardening: timeline-frames.html is still flaky

Test looks much better on the flakiness dashboard after a rebase at
blink r183180, but it's still flaking on various bots.

BUG=407915
TBR=loislo

Review URL: https://codereview.chromium.org/625893004

git-svn-id: svn://svn.chromium.org/blink/trunk@183205 bbb929c8-8fbe-4397-9dbb-9b2b20218538