Set local function type as uninstantiated when applicable (fix issue 12127).

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 25677)
+++ runtime/vm/object.cc	(working copy)
@@ -10504,6 +10504,13 @@
 }
 
 
+void Type::ResetIsFinalized() const {
+  ASSERT(IsFinalized());
+  set_type_state(RawType::kBeingFinalized);
+  SetIsFinalized();
+}
+
+
 void Type::set_is_being_finalized() const {
   ASSERT(!IsFinalized() && !IsBeingFinalized());
   set_type_state(RawType::kBeingFinalized);