Changed interfaces to abstract classes in utils.

utils/tests/string_encoding/dunit.dart

 #!/usr/bin/env 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("dunit");
 
 typedef void Test();
 typedef TestResult SynchTest();
 typedef Future<TestResult> AsynchTest();
@@ skipping 38 matching lines @@
       print("FAIL -- TESTS RUN: ${results.length}");
       print("        PASSED: ${passedTests}");
       print("        FAILED: ${failures}");
       print("        ERRORS: ${errors}");
     }
   }
 
   List<SynchTest> _tests;
 }
 
-interface TestResult {
+abstract class TestResult {
   String get testDescription;
 }
 
 class PassedTest implements TestResult {
   const PassedTest(String this._testDescription);
   String get testDescription => _testDescription;
   final String _testDescription;
   String toString() => _testDescription;
 }
 
@@ skipping 40 matching lines @@
         tearDown();
         return new TestError(description, x, stacktrace);
       }
     });
   }
 
   abstract void registerTests(TestSuite suite);
   void setUp() {}
   void tearDown() {}
 }