Fix tools/test.dart dartc/junit_tests callback type error.

tools/testing/dart/test_suite.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_suite");
 
 #import("status_file_parser.dart");
 #import("test_runner.dart");
 #import("multitest.dart");
 
@@ skipping 846 matching lines @@
         '-classpath', classPath,
         '-Dcom.google.dart.runner.d8=$d8',
         '-Dcom.google.dart.corelib.SharedTests.test_py=$dartDir/tools/test.py',
         'org.junit.runner.JUnitCore'];
     args.addAll(testClasses);
           
     doTest(new TestCase(suiteName,
                         'java',
                         args,
                         configuration,
-                        (){},
+                        completeHandler,
                         new Set<String>.from([PASS])));
     doDone();
   }
 
+  void completeHandler(TestCase testCase) {
+  }
+
   void computeClassPath() {
     classPath = Strings.join(
         ['$buildDir/compiler/lib/dartc.jar',
          '$buildDir/compiler/lib/corelib.jar',
          '$buildDir/compiler-tests.jar',
          '$buildDir/closure_out/compiler.jar',
          // Third party libraries.
          'third_party/args4j/2.0.12/args4j-2.0.12.jar',
          'third_party/guava/r09/guava-r09.jar',
          'third_party/json/r2_20080312/json.jar',
@@ skipping 141 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);
   }
 }