Fix some type warnings in the test scripts, that show up when using the editor.

tools/testing/dart/test_suite.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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 738 matching lines @@
       case 'dart2js':
       case 'dartc':
         return 'text/javascript';
       default:
         Expect.fail('Non-web runtime, so no scriptType for: ' +
             '${configuration["compiler"]}');
         return null;
     }
   }
   
-  String get hasRuntime() {
+  bool get hasRuntime() {
     switch(configuration['runtime']) {
       case null:
         Expect.fail("configuration['runtime'] is not set");
       case 'none':
         return false;
       default:
         return true;
     }
   }
 
@@ skipping 610 matching lines @@
  * $noCrash tests are expected to be flaky but not crash
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
 """;
     print(report);
    }
 }