Refactoring: Unify all mocks in auto roll tests.

This allows to use shell command, readline and url
expectations in the same list, which makes their interaction
more explicit.

TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/533693002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23624 ce2b1a6d-e550-0410-aec6-3dcde31c8c00