Deflake svg/animations/repeatn-event-2a.svg

svg/animations/repeatn-event-2a.svg is currently flaky on our trybots [1],
particularly the debug and asan bots. This is an experimental patch to
increase reliability by bumping the timeout in this patch from 10ms to
30ms.

[1] http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=svg%2Fanimations%2Frepeatn-event-2a.svg

NOTRY=true
TBR=dstockwell

Review URL: https://codereview.chromium.org/141073010

git-svn-id: svn://svn.chromium.org/blink/trunk@165357 bbb929c8-8fbe-4397-9dbb-9b2b20218538