fix how DDC finds its undefined constant

pkg/dev_compiler/test/codegen_expected/node_modules.js

Index: pkg/dev_compiler/test/codegen_expected/node_modules.js
diff --git a/pkg/dev_compiler/test/codegen_expected/node_modules.js b/pkg/dev_compiler/test/codegen_expected/node_modules.js
index bc44cde4575402b972bae19aee5581a845af3f5c..976b5f0b091aa9f80e23e28fa4664e10198fce6a 100644
--- a/pkg/dev_compiler/test/codegen_expected/node_modules.js
+++ b/pkg/dev_compiler/test/codegen_expected/node_modules.js
@@ -12,25 +12,33 @@ node_modules.Callback = dart.typedef('Callback', () => dart.fnTypeFuzzy(dart.voi
 node_modules.A = class A extends core.Object {};
 (node_modules.A.new = function() {
 }).prototype = node_modules.A.prototype;
+dart.addTypeTests(node_modules.A);
 node_modules._A = class _A extends core.Object {};
 (node_modules._A.new = function() {
 }).prototype = node_modules._A.prototype;
+dart.addTypeTests(node_modules._A);
+const _is_B_default = Symbol('_is_B_default');
 node_modules.B$ = dart.generic(T => {
   class B extends core.Object {}
   (B.new = function() {
   }).prototype = B.prototype;
   dart.addTypeTests(B);
+  B.prototype[_is_B_default] = true;
   return B;
 });
 node_modules.B = B();
+dart.addTypeTests(node_modules.B, _is_B_default);
+const _is__B_default = Symbol('_is__B_default');
 node_modules._B$ = dart.generic(T => {
   class _B extends core.Object {}
   (_B.new = function() {
   }).prototype = _B.prototype;
   dart.addTypeTests(_B);
+  _B.prototype[_is__B_default] = true;
   return _B;
 });
 node_modules._B = _B();
+dart.addTypeTests(node_modules._B, _is__B_default);
 node_modules.f = function() {
 };
 dart.fn(node_modules.f, VoidTodynamic());