Implement 'edit.getRefactoring' for rename refactoring.

pkg/analysis_server/test/services/refactoring/extract_local_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.refactoring.extract_local;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol2.dart';
 import 'package:analysis_server/src/services/correction/change.dart';
@@ skipping 186 matching lines @@
 main() {
   int a = 1 + 2;
 }
 ''');
     _createRefactoringForString('1 + 2');
     expect(refactoring.refactoringName, 'Extract Local Variable');
     // null
     refactoring.name = null;
     assertRefactoringStatus(
         refactoring.checkName(),
-        RefactoringProblemSeverity.ERROR,
+        RefactoringProblemSeverity.FATAL,
         expectedMessage: "Variable name must not be null.");
     // empty
     refactoring.name = '';
     assertRefactoringStatus(
         refactoring.checkName(),
-        RefactoringProblemSeverity.ERROR,
+        RefactoringProblemSeverity.FATAL,
         expectedMessage: "Variable name must not be empty.");
     // OK
     refactoring.name = 'res';
     assertRefactoringStatusOK(refactoring.checkName());
   }
 
   test_completeStatementExpression() {
     indexTestUnit('''
 main(p) {
   p.toString();
@@ skipping 673 matching lines @@
     int length = search.length;
     _createRefactoring(offset, length);
   }
 
   void _createRefactoringWithSuffix(String selectionSearch, String suffix) {
     int offset = findOffset(selectionSearch + suffix);
     int length = selectionSearch.length;
     _createRefactoring(offset, length);
   }
 }