Slightly generalize AddCheckConstantFunction.

src/ast.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1566 matching lines @@
   Expression* expression() const { return expression_; }
   ZoneList<Expression*>* arguments() const { return arguments_; }
   virtual int position() const { return pos_; }
 
   void RecordTypeFeedback(TypeFeedbackOracle* oracle,
                           CallKind call_kind);
   virtual SmallMapList* GetReceiverTypes() { return &receiver_types_; }
   virtual bool IsMonomorphic() { return is_monomorphic_; }
   CheckType check_type() const { return check_type_; }
   Handle<JSFunction> target() { return target_; }
+
+  // A cache for the holder, set as a side effect of computing the target of the
+  // call. Note that it contains the null handle when the receiver is the same
+  // as the holder!
   Handle<JSObject> holder() { return holder_; }
+
   Handle<JSGlobalPropertyCell> cell() { return cell_; }
 
   bool ComputeTarget(Handle<Map> type, Handle<String> name);
   bool ComputeGlobalTarget(Handle<GlobalObject> global, LookupResult* lookup);
 
   // Bailout support.
   int ReturnId() const { return return_id_; }
 
 #ifdef DEBUG
   // Used to assert that the FullCodeGenerator records the return site.
@@ skipping 1386 matching lines @@
  private:
   Isolate* isolate_;
   Zone* zone_;
   Visitor visitor_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_