Rename Closure instance field type_arguments_ to instantiator_.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 5af05c99d4154258b541ac7228f32655f6656ae5..f5492312d7f8f0c195f6e936bd6fab535cf1a206 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -398,17 +398,16 @@ static void UpdateTypeTestCache(
   }
   const Class& instance_class = Class::Handle(instance.clazz());
   Object& instance_class_id_or_function = Object::Handle();
+  TypeArguments& instance_type_arguments = TypeArguments::Handle();
   if (instance_class.IsClosureClass()) {
     instance_class_id_or_function = Closure::Cast(instance).function();
+    instance_type_arguments = Closure::Cast(instance).instantiator();
   } else {
     instance_class_id_or_function = Smi::New(instance_class.id());
+    if (instance_class.NumTypeArguments() > 0) {
+      instance_type_arguments = instance.GetTypeArguments();
+    }
   }
-  TypeArguments& instance_type_arguments = TypeArguments::Handle();
-  if (instance_class.IsClosureClass() ||
-      (instance_class.NumTypeArguments() > 0)) {
-    instance_type_arguments = instance.GetTypeArguments();
-  }
-
   const intptr_t len = new_cache.NumberOfChecks();
   if (len >= FLAG_max_subtype_cache_entries) {
     return;