fix how DDC finds its undefined constant

pkg/dev_compiler/test/codegen_expected/unresolved_names.js

 define(['dart_sdk'], function(dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const unresolved_names = Object.create(null);
   let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.fnType(dart.dynamic, [])))();
   unresolved_names.C = class C extends core.Object {};
   (unresolved_names.C.new = function() {
   }).prototype = unresolved_names.C.prototype;
+  dart.addTypeTests(unresolved_names.C);
   unresolved_names.main = function() {
     new (dart.throw(Error("compile error: unresolved constructor: dynamic.<unnamed>")))();
     new (dart.throw(Error("compile error: unresolved constructor: C.bar")))();
     core.print(dart.throw(Error("compile error: unresolved identifier: baz")));
     core.print(dart.dload(unresolved_names.C, 'quux'));
   };
   dart.fn(unresolved_names.main, VoidTodynamic());
   dart.trackLibraries("unresolved_names", {
     "unresolved_names.dart": unresolved_names
   }, null);
   // Exports:
   return {
     unresolved_names: unresolved_names
   };
 });