VM: Implement closure calls as instance calls.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 34916)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -2160,6 +2160,13 @@
 }
 
 
+bool PolymorphicInstanceCallInstr::HasSingleDispatcherTarget() const {
+  if (!ic_data().HasOneTarget()) return false;
+  const Function& target = Function::Handle(ic_data().GetTargetAt(0));
+  return target.IsNoSuchMethodDispatcher() || target.IsInvokeFieldDispatcher();
+}
+
+
 LocationSummary* StaticCallInstr::MakeLocationSummary(bool optimizing) const {
   return MakeCallSummary();
 }