Make webkit test output comparison compatible to stress testing.

In stress testing, the output is repeated several times. In this case, it is now compared several times to the actual output.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18062002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15369 ce2b1a6d-e550-0410-aec6-3dcde31c8c00