Add UInt32 and UInt31 types to better infer bit operations.

tests/compiler/dart2js/list_tracer_test.dart

 // Copyright (c) 2013, 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 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import
     '../../../sdk/lib/_internal/compiler/implementation/types/types.dart'
     show ContainerTypeMask, TypeMask;
 
@@ skipping 196 matching lines @@
     checkType('listUsedWithCascade', typesTask.numType);
     checkType('listUsedInClosure', typesTask.numType);
     checkType('listPassedToSelector', typesTask.numType);
     checkType('listReturnedFromSelector', typesTask.numType);
     checkType('listUsedWithAddAndInsert', typesTask.numType);
     checkType('listUsedWithConstraint', typesTask.intType);
     checkType('listEscapingFromSetter', typesTask.numType);
     checkType('listUsedInLocal', typesTask.numType);
     checkType('listEscapingInSetterValue', typesTask.numType);
     checkType('listEscapingInIndex', typesTask.numType);
-    checkType('listEscapingInIndexSet', typesTask.intType);
+    checkType('listEscapingInIndexSet', typesTask.uint31Type);
     checkType('listEscapingTwiceInIndexSet', typesTask.numType);
     checkType('listSetInNonFinalField', typesTask.numType);
-    checkType('listWithChangedLength', typesTask.intType.nullable());
+    checkType('listWithChangedLength', typesTask.uint31Type.nullable());
 
     checkType('listPassedToClosure', typesTask.dynamicType);
     checkType('listReturnedFromClosure', typesTask.dynamicType);
     checkType('listUsedWithNonOkSelector', typesTask.dynamicType);
     checkType('listPassedAsOptionalParameter', typesTask.numType);
     checkType('listPassedAsNamedParameter', typesTask.numType);
 
     if (!allocation.contains('filled')) {
       checkType('listUnset', new TypeMask.nonNullEmpty());
-      // TODO(ngeoffray): Re-enable this test.
-      // checkType('listOnlySetWithConstraint', new TypeMask.nonNullEmpty());
+      checkType('listOnlySetWithConstraint', new TypeMask.nonNullEmpty());
     }
   }));
 }