Fix problems that occur in checked mode.

tests/utils/unittest_test.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.
 
 #library('unittestTest');
 
 #import('../../lib/unittest/unittest.dart');
 
 
 doesNotThrow() {}
 doesThrow() { throw 'X'; }
 
 int errorCount;
 String errorString;
 var testHandler;
 
 class MyFailureHandler extends DefaultFailureHandler {
   void fail(String reason) {
     ++errorCount;
     errorString = reason;
   }
 }
 
-void shouldFail(var value, Matcher matcher, String expected) {
+void shouldFail(var value, Matcher matcher, expected) {
   errorCount = 0;
   errorString = '';
   configureExpectHandler(testHandler);
   expect(value, matcher);
   configureExpectHandler(null);
   expect(errorCount, equals(1));
   if (expected is String)
     expect(errorString, equalsIgnoringWhitespace(expected));
   else
    expect(errorString, expected);
@@ skipping 409 matching lines @@
     test('allOf', () {
       shouldPass(1, allOf([lessThan(10), greaterThan(0)]));
       shouldFail(-1, allOf([lessThan(10), greaterThan(0)]),
           "Expected: (a value less than <10> and a value greater than <0>) "
           "but: a value greater than <0> was <-1>");
     });
   });
 }