Translate Java's @Override into Dart's @override.

pkg/analyzer/test/generated/test_support.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.test_support;
 
 import 'package:analyzer/src/generated/java_core.dart';
@@ skipping 259 matching lines @@
     return false;
   }
 
   /**
    * Return `true` if at least one error has been gathered.
    *
    * @return `true` if at least one error has been gathered
    */
   bool get hasErrors => _errors.length > 0;
 
+  @override
   void onError(AnalysisError error) {
     if (_rawSource != null) {
       int left = error.offset;
       int right = left + error.length - 1;
       _markedSource = "${_rawSource.substring(0, left)}^${_rawSource.substring(left, right)}^${_rawSource.substring(right)}";
     }
     _errors.add(error);
   }
 
   /**
@@ skipping 562 matching lines @@
   Source resolveRelative(Uri uri) {
     throw new UnsupportedOperationException();
   }
   UriKind get uriKind {
     throw new UnsupportedOperationException();
   }
   TimestampedData<String> get contents {
     throw new UnsupportedOperationException();
   }
 }