Fix issues when changing FLAG_concurrent_recompilation after init.

R=jarin@chromium.org
BUG=356053
LOG=N

Review URL: https://codereview.chromium.org/210363005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20228 ce2b1a6d-e550-0410-aec6-3dcde31c8c00