Mark CollectCpuProfile as flaky.

R=machenbach@chromium.org
BUG=v8:2999
LOG=N

Review URL: https://codereview.chromium.org/208043002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20157 ce2b1a6d-e550-0410-aec6-3dcde31c8c00