Update test scripts to deal with current VM behavior on optional constructor arguments.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2011, 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("test_runner");
 
 #import("status_file_parser.dart");
 #import("test_progress.dart");
 
 /**
@@ skipping 20 matching lines @@
 
   TestCase(this.displayName,
            this.executablePath,
            this.arguments,
            this.timeout,
            this.completedHandler,
            this.expectedOutcomes,
            [isNegative = false])
       : this.isNegative = isNegative {
     if (!isNegative) {
-      isNegative = displayName.contains("NegativeTest");
+      this.isNegative = displayName.contains("NegativeTest");
     }
     commandLine = executablePath;
     for (var arg in arguments) {
       commandLine += " " + arg;
     }
   }
 
   void completed() { completedHandler(this); }
 }
 
@@ skipping 142 matching lines @@
       numProcesses++;
     }
   }
 
   runTest(TestCase test) {
     progress.testAdded();
     tests.add(test);
     tryRunTest();
   }
 }