Change TypeMask.base to be a ClassElement.

tests/compiler/dart2js/compiler_helper.dart

 // Copyright (c) 2012, 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.
 // Test constant folding.
 
 library compiler_helper;
 
 import 'dart:async';
 import "package:expect/expect.dart";
 
@@ skipping 130 matching lines @@
                             [String how = 'nonNullExact']) {
   var sourceName = buildSourceString(name);
   var element = compiler.mainApp.find(sourceName);
   if (element == null) {
     element = compiler.interceptorsLibrary.find(sourceName);
   }
   if (element == null) {
     element = compiler.coreLibrary.find(sourceName);
   }
   Expect.isNotNull(element, 'Could not locate $name');
-  var dartType = element.computeType(compiler);
   switch (how) {
-    case 'exact': return new types.TypeMask.exact(dartType);
-    case 'nonNullExact': return new types.TypeMask.nonNullExact(dartType);
-    case 'subclass': return new types.TypeMask.subclass(dartType);
-    case 'nonNullSubclass': return new types.TypeMask.nonNullSubclass(dartType);
-    case 'subtype': return new types.TypeMask.subtype(dartType);
-    case 'nonNullSubtype': return new types.TypeMask.nonNullSubtype(dartType);
+    case 'exact': return new types.TypeMask.exact(element);
+    case 'nonNullExact': return new types.TypeMask.nonNullExact(element);
+    case 'subclass': return new types.TypeMask.subclass(element);
+    case 'nonNullSubclass': return new types.TypeMask.nonNullSubclass(element);
+    case 'subtype': return new types.TypeMask.subtype(element);
+    case 'nonNullSubtype': return new types.TypeMask.nonNullSubtype(element);
   }
   Expect.fail('Unknown HType constructor $how');
 }
 
 ssa.HType findHType(compiler, String name, [String how = 'nonNullExact']) {
   return new ssa.HType.fromMask(findTypeMask(compiler, name, how), compiler);
 }
 
 String anyIdentifier = "[a-zA-Z][a-zA-Z0-9]*";
 
@@ skipping 45 matching lines @@
   final xRe = new RegExp('\\bx\\b');
   regexp = regexp.replaceAll(xRe, '(?:$anyIdentifier)');
   final spaceRe = new RegExp('\\s+');
   regexp = regexp.replaceAll(spaceRe, '(?:\\s*)');
   if (shouldMatch) {
     Expect.isTrue(new RegExp(regexp).hasMatch(generated));
   } else {
     Expect.isFalse(new RegExp(regexp).hasMatch(generated));
   }
 }