media/media-document-audio-repaint.html is flaky

BUG=353934
TBR=enne@chromium.org

Review URL: https://codereview.chromium.org/197873036

git-svn-id: svn://svn.chromium.org/blink/trunk@169528 bbb929c8-8fbe-4397-9dbb-9b2b20218538