The justification for doing this is to reduce the size of the graph and
therefore speedup later phases of compilation. The control reducer also
obviates the need to run the PhiReducer, since it subsumes it.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/681263004

Cr-Commit-Position: refs/heads/master@{#24986}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24986 ce2b1a6d-e550-0410-aec6-3dcde31c8c00