Gardening: Mark svg/repaint/image-animation-with-zoom.html as flaky

TBR=pdr@chromium.org
BUG=377950

Review URL: https://codereview.chromium.org/307543003

git-svn-id: svn://svn.chromium.org/blink/trunk@174886 bbb929c8-8fbe-4397-9dbb-9b2b20218538