fix #603, support mock objects

test/codegen_expected/language/override_inheritance_no_such_method_test_13_multi.js

 dart_library.library('language/override_inheritance_no_such_method_test_13_multi', null, /* Imports */[
   'dart_sdk'
 ], function load__override_inheritance_no_such_method_test_13_multi(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const override_inheritance_no_such_method_test_13_multi = Object.create(null);
   let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
   override_inheritance_no_such_method_test_13_multi.A = class A extends core.Object {};
   override_inheritance_no_such_method_test_13_multi.I = class I extends core.Object {};
   override_inheritance_no_such_method_test_13_multi.Class1 = class Class1 extends override_inheritance_no_such_method_test_13_multi.A {};
   override_inheritance_no_such_method_test_13_multi.Class1[dart.implements] = () => [override_inheritance_no_such_method_test_13_multi.I];
   override_inheritance_no_such_method_test_13_multi.B = class B extends core.Object {
     noSuchMethod(_) {
       return null;
     }
+    method13() {
+      return this.noSuchMethod(new dart.InvocationImpl('method13', [], {isMethod: true}));
+    }
   };
-  override_inheritance_no_such_method_test_13_multi.Class2 = class Class2 extends override_inheritance_no_such_method_test_13_multi.B {};
+  override_inheritance_no_such_method_test_13_multi.Class2 = class Class2 extends override_inheritance_no_such_method_test_13_multi.B {
+    method13() {
+      return this.noSuchMethod(new dart.InvocationImpl('method13', [], {isMethod: true}));
+    }
+  };
   override_inheritance_no_such_method_test_13_multi.main = function() {
     new override_inheritance_no_such_method_test_13_multi.Class1();
     new override_inheritance_no_such_method_test_13_multi.Class2();
   };
   dart.fn(override_inheritance_no_such_method_test_13_multi.main, VoidTodynamic());
   // Exports:
   exports.override_inheritance_no_such_method_test_13_multi = override_inheritance_no_such_method_test_13_multi;
 });