Instead, we block concurrent recompilation until unblocked. This makes
affected tests more predictable and run shorter.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/26758003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17199 ce2b1a6d-e550-0410-aec6-3dcde31c8c00