Gardening: Mark animated-path-inside-transformed-html.xhtml as flaky

TBR=enne@chromium.org,davve@opera.com
BUG=367846
NOTRY=true

Review URL: https://codereview.chromium.org/256703007

git-svn-id: svn://svn.chromium.org/blink/trunk@172781 bbb929c8-8fbe-4397-9dbb-9b2b20218538