I believe I've now twice down the experiment of disabling DCE in the FTL,
only to realize that this can't work, and that DCE is needed. I'd kind of
like to not make that mistake again.

* dfg/DFGPlan.cpp:
(JSC::DFG::Plan::compileInThreadImpl):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153266 268f45cc-cd09-0410-ab3c-d52691b4dbfc