Fix equality between subclasses of Source

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.
 
 library analyzer.test.generated.test_support;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart' show AstNode, SimpleIdentifier;
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 582 matching lines @@
   }
 
   @override
   int get modificationStamp =>
       generateExceptionOnRead ? -1 : _modificationStamp;
 
   String get shortName {
     return _name;
   }
 
-  Uri get uri {
-    throw new UnsupportedOperationException();
-  }
+  Uri get uri => new Uri.file(_name);
 
   UriKind get uriKind {
     throw new UnsupportedOperationException();
   }
 
   bool operator ==(Object other) {
     if (other is TestSource) {
       return other._name == _name;
     }
     return false;
@@ skipping 37 matching lines @@
     return UriKind.FILE_URI;
   }
 
   bool operator ==(Object other) {
     if (other is TestSource) {
       return other.uri == uri;
     }
     return false;
   }
 }