fix how DDC finds its undefined constant

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 210 matching lines @@
         boolClass = _getLibrary(c, 'dart:core').getType('bool'),
         intClass = _getLibrary(c, 'dart:core').getType('int'),
         doubleClass = _getLibrary(c, 'dart:core').getType('double'),
         numClass = _getLibrary(c, 'dart:core').getType('num'),
         nullClass = _getLibrary(c, 'dart:core').getType('Null'),
         objectClass = _getLibrary(c, 'dart:core').getType('Object'),
         stringClass = _getLibrary(c, 'dart:core').getType('String'),
         functionClass = _getLibrary(c, 'dart:core').getType('Function'),
         privateSymbolClass =
             _getLibrary(c, 'dart:_internal').getType('PrivateSymbol'),
-        dartJSLibrary = _getLibrary(c, 'dart:js'),
-        _undefinedConstant =
-            _getLibrary(c, 'dart:_runtime').publicNamespace.get('undefined') {
-    assert(_undefinedConstant != null);
+        dartJSLibrary = _getLibrary(c, 'dart:js') {
     typeRep = new JSTypeRep(rules, types);
   }
 
   Element get currentElement => _currentElements.last;
 
   LibraryElement get currentLibrary => currentElement.library;
 
   /// The main entry point to JavaScript code generation.
   ///
   /// Takes the metadata for the build unit, as well as resolved trees and
@@ skipping 2241 matching lines @@
     if (param is DefaultFormalParameter && param.defaultValue != null) {
       var defaultValue = param.defaultValue;
       return _isJSUndefined(defaultValue) ? null : _visit(defaultValue);
     } else {
       return new JS.LiteralNull();
     }
   }
 
   bool _isJSUndefined(Expression expr) {
     expr = expr is AsExpression ? expr.expression : expr;
-    return expr is Identifier && expr.staticElement == _undefinedConstant;
+    if (expr is Identifier) {
+      var element = expr.staticElement;
+      return isSdkInternalRuntime(element.library) &&
+          element.name == 'undefined';
+    }
+    return false;
   }
 
   JS.Fun _emitNativeFunctionBody(MethodDeclaration node) {
     String name =
         getAnnotationName(node.element, isJSAnnotation) ?? node.name.name;
     if (node.isGetter) {
       return new JS.Fun([], js.statement('{ return this.#; }', [name]));
     } else if (node.isSetter) {
       var params =
           _emitFormalParameterList(node.parameters, destructure: false);
@@ skipping 1625 matching lines @@
   void _emitTopLevelFields(List<VariableDeclaration> fields) {
     _moduleItems.add(_emitLazyFields(currentLibrary, fields));
   }
 
   /// Treat dart:_runtime fields as safe to eagerly evaluate.
   // TODO(jmesserly): it'd be nice to avoid this special case.
   void _emitInternalSdkFields(List<VariableDeclaration> fields) {
     for (var field in fields) {
       // Skip our magic undefined constant.
       var element = field.element as TopLevelVariableElement;
-      if (element.getter == _undefinedConstant) continue;
+      if (element.name == 'undefined') continue;
       _moduleItems.add(annotate(
           js.statement('# = #;',
               [_emitTopLevelName(field.element), _visitInitializer(field)]),
           field,
           field.element));
     }
   }
 
   JS.Expression _visitInitializer(VariableDeclaration node) {
     var value = _annotatedNullCheck(node.element)
@@ skipping 1943 matching lines @@
   '~/': 'floorDivide',
   '*': 'times',
   '%': 'modulo',
   '|': 'bitOr',
   '^': 'bitXor',
   '&': 'bitAnd',
   '<<': 'leftShift',
   '>>': 'rightShift',
   '~': 'bitNot'
 };