[Sheriff] Mark flaky test on windows.

BUG=v8:2999
TBR=yangguo@chromium.org

Review URL: https://codereview.chromium.org/68773007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17643 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
CLOCK_REALTIME is 0 on Linux, use -1 for invalid clock id.

TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/70133003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17644 ce2b1a6d-e550-0410-aec6-3dcde31c8c00