[turbofan] Disable optimization of dynamic lookup slots.

Note that this essentially disables optimization of "with" as well.

R=hablich@chromium.org
BUG=chromium:491897,chromium:491018
LOG=N

Review URL: https://codereview.chromium.org/1158343003

Cr-Commit-Position: refs/heads/master@{#28725}

src/ast-numbering.cc

@@ -155,7 +155,7 @@ void AstNumberingVisitor::VisitRegExpLiteral(RegExpLiteral* node) {
 void AstNumberingVisitor::VisitVariableProxy(VariableProxy* node) {
   IncrementNodeCount();
   if (node->var()->IsLookupSlot()) {
-    DisableCrankshaft(kReferenceToAVariableWhichRequiresDynamicLookup);
+    DisableOptimization(kReferenceToAVariableWhichRequiresDynamicLookup);
   }
   ReserveFeedbackSlots(node);
   node->set_base_id(ReserveIdRange(VariableProxy::num_ids()));