Properly handle instantiator when allocating or cloning closure instance.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 50144c20cfc8402d21eca99731214f54b56b35c5..84656ed580b6ffe27148810bafbc507befec56b3 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -8302,17 +8302,17 @@ class LinkedHashMap : public Instance {
 
 class Closure : public Instance {
  public:
+  RawTypeArguments* instantiator() const { return raw_ptr()->instantiator_; }
+  static intptr_t instantiator_offset() {
+    return OFFSET_OF(RawClosure, instantiator_);
+  }
+
   RawFunction* function() const { return raw_ptr()->function_; }
   static intptr_t function_offset() { return OFFSET_OF(RawClosure, function_); }
 
   RawContext* context() const { return raw_ptr()->context_; }
   static intptr_t context_offset() { return OFFSET_OF(RawClosure, context_); }
 
-  RawTypeArguments* instantiator() const { return raw_ptr()->instantiator_; }
-  static intptr_t instantiator_offset() {
-    return OFFSET_OF(RawClosure, instantiator_);
-  }
-
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawClosure));
   }
@@ -8324,7 +8324,8 @@ class Closure : public Instance {
     return true;
   }
 
-  static RawClosure* New(const Function& function,
+  static RawClosure* New(const TypeArguments& instantiator,
+                         const Function& function,
                          const Context& context,
                          Heap::Space space = Heap::kNew);