Extend existing blink test expectations for slow tests.

The test plugins/js-from-destroy.html has crash and timeout expectations for some configurations but not on windows release. Add 'slow', since there is a timeout only on the v8 waterfall and only for windows release.

BUG=webkit.org/b/48655
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/20082002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15852 ce2b1a6d-e550-0410-aec6-3dcde31c8c00