Replace InstanceSetterComp instruction with a plain instance call.

vm/intermediate_language.cc

Index: vm/intermediate_language.cc
===================================================================
--- vm/intermediate_language.cc	(revision 10227)
+++ vm/intermediate_language.cc	(working copy)
@@ -799,13 +799,6 @@
 }
 
 
-RawAbstractType* InstanceSetterComp::StaticType() const {
-  // This computation does not have a result value.
-  UNREACHABLE();
-  return AbstractType::null();
-}
-
-
 RawAbstractType* LoadInstanceFieldComp::StaticType() const {
   if (FLAG_enable_type_checks) {
     return field().type();