Mark four tests flaky.

- web-animations-api/change-in-animation-frame.html [ Failure Pass ]
- compositing/plugins/invalidate_rect.html [ Failure Pass ]
- virtual/softwarecompositing/plugins/invalidate_rect.html [ Failure Pass ]
- svg/custom/js-late-pattern-and-object-creation.svg [ ImageOnlyFailure Pass ]

BUG=357437,357438,357439
TBR=enne@chromium.org

Review URL: https://codereview.chromium.org/216023002

git-svn-id: svn://svn.chromium.org/blink/trunk@170240 bbb929c8-8fbe-4397-9dbb-9b2b20218538