Rename Closure instance field type_arguments_ to instantiator_.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 9023b2f4256329a2b5df6364409b5cd61919d5b9..d43bc3559fe1f0dc5d583fdbf8a2d33d65d0693d 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -8296,21 +8296,14 @@ class LinkedHashMap : public Instance {
 class Closure : public Instance {
  public:
   RawFunction* function() const { return raw_ptr()->function_; }
-  void set_function(const Function& function) const {
-    // TODO(regis): Only used from deferred_objects.cc. Remove once fixed.
-    StorePointer(&raw_ptr()->function_, function.raw());
-  }
   static intptr_t function_offset() { return OFFSET_OF(RawClosure, function_); }
 
   RawContext* context() const { return raw_ptr()->context_; }
-  void set_context(const Context& context) const {
-    // TODO(regis): Only used from deferred_objects.cc. Remove once fixed.
-    StorePointer(&raw_ptr()->context_, context.raw());
-  }
   static intptr_t context_offset() { return OFFSET_OF(RawClosure, context_); }
 
-  static intptr_t type_arguments_offset() {
-    return OFFSET_OF(RawClosure, type_arguments_);
+  RawTypeArguments* instantiator() const { return raw_ptr()->instantiator_; }
+  static intptr_t instantiator_offset() {
+    return OFFSET_OF(RawClosure, instantiator_);
   }
 
   static intptr_t InstanceSize() {