Revert "Convert unittest to use "package:" imports."

pkg/unittest/test/mock_regexp_negative_test.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 mock_regexp_negative_test;
-import 'package:unittest/unittest.dart';
-import 'package:unittest/mock.dart';
+import '../../../pkg/unittest/lib/unittest.dart';
+import '../../../pkg/unittest/lib/mock.dart';
 
 main() {
   test('Mocking: RegExp CallMatcher bad', () {
-    var m = new Mock();
-    m.when(callsTo(matches('^[A-Z]'))).
-           alwaysThrow('Method names must start with lower case.');
-    m.Test();
+    var m = new Mock();           
+    m.when(callsTo(matches('^[A-Z]'))).          
+           alwaysThrow('Method names must start with lower case.');      
+    m.Test();         
   });
 }