Fix for extracting local variable in if-else-if statements.

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/protocol.dart';
 import 'package:analysis_server/src/services/refactoring/extract_local.dart';
@@ skipping 750 matching lines @@
     return _assertSuccessfulRefactoring('''
 main() {
   print((x) {
     var res = x.y;
     return res * res + 1;
   });
 }
 ''');
   }
 
+  test_singleExpression_inIfElseIf() {
+    indexTestUnit('''
+main(int p) {
+  if (p == 1) {
+    print(1);
+  } else if (p == 2) {
+    print(2);
+  }
+}
+''');
+    _createRefactoringForString('2');
+    // apply refactoring
+    return _assertSuccessfulRefactoring('''
+main(int p) {
+  var res = 2;
+  if (p == 1) {
+    print(1);
+  } else if (p == res) {
+    print(res);
+  }
+}
+''');
+  }
+
   test_singleExpression_inMethod() {
     indexTestUnit('''
 class A {
   main() {
     print(1 + 2);
   }
 }
 ''');
     _createRefactoringForString('1 + 2');
     // apply refactoring
@@ skipping 186 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);
   }
 }