Fix for the prefix/suffix diff computing.

pkg/analysis_server/test/services/correction/diff_test.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 test.services.correction.diff;
-
-import 'package:analysis_server/src/services/correction/diff.dart';
-import 'package:unittest/unittest.dart';
-
-import '../../reflective_tests.dart';
-
-
-main() {
-  groupSep = ' | ';
-  runReflectiveTests(DiffTest);
-}
-
-@ReflectiveTestCase()
-class DiffTest {
-  void test_findCommonPrefix() {
-    expect(findCommonPrefix('abc', 'xyz'), 0);
-    expect(findCommonPrefix('1234abcdef', '1234xyz'), 4);
-    expect(findCommonPrefix('123', '123xyz'), 3);
-  }
-
-  void test_findCommonSuffix() {
-    expect(findCommonSuffix('abc', 'xyz'), 0);
-    expect(findCommonSuffix('abcdef1234', 'xyz1234'), 4);
-    expect(findCommonSuffix('123', 'xyz123'), 3);
-  }
-}