[crankshaft] Add baseline implementation of for-of.

src/ast-numbering.cc

Index: src/ast-numbering.cc
diff --git a/src/ast-numbering.cc b/src/ast-numbering.cc
index 7338cc6724219678852d5a90c40155b5a62e53ad..b3945c3ac38575301831063c0ee436a298e38ffd 100644
--- a/src/ast-numbering.cc
+++ b/src/ast-numbering.cc
@@ -389,7 +389,6 @@ void AstNumberingVisitor::VisitForInStatement(ForInStatement* node) {
 
 void AstNumberingVisitor::VisitForOfStatement(ForOfStatement* node) {
   IncrementNodeCount();
-  DisableCrankshaft(kForOfStatement);
   node->set_base_id(ReserveIdRange(ForOfStatement::num_ids()));
   Visit(node->assign_iterator());
   Visit(node->next_result());