Use async/await in refactorings.

pkg/analysis_server/lib/src/services/refactoring/refactoring_internal.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 services.src.refactoring;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
@@ skipping 27 matching lines @@
 }
 
 
 /**
  * Abstract implementation of [Refactoring].
  */
 abstract class RefactoringImpl implements Refactoring {
   final List<String> potentialEditIds = <String>[];
 
   @override
-  Future<RefactoringStatus> checkAllConditions() {
+  Future<RefactoringStatus> checkAllConditions() async {
     RefactoringStatus result = new RefactoringStatus();
-    return checkInitialConditions().then((status) {
-      result.addStatus(status);
-      if (result.hasFatalError) {
-        return result;
-      }
-      return checkFinalConditions().then((status) {
-        result.addStatus(status);
-        return result;
-      });
-    });
+    result.addStatus(await checkInitialConditions());
+    if (result.hasFatalError) {
+      return result;
+    }
+    result.addStatus(await checkFinalConditions());
+    return result;
   }
 }
 
 
 /**
  * The [SourceRange] in some [Source].
  */
 class SourceReference {
   final String file;
   final SourceRange range;
@@ skipping 33 matching lines @@
   /**
    * Returns the [SourceEdit] to replace this reference.
    */
   SourceEdit createEdit(String newText, {String id}) {
     return newSourceEdit_range(range, newText, id: id);
   }
 
   @override
   String toString() => '${file}@${range}';
 }