Start making server strong mode clean

pkg/analysis_server/test/edit/refactoring_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.edit.refactoring;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
@@ skipping 635 matching lines @@
 // end
   res(a, b);
 }
 
 void res(int a, int b) {
   print(a + b);
 }
 ''');
   }
 
-  Future<Response> _computeChange() {
-    return _prepareOptions().then((_) {
-      // send request with the options
-      return _sendExtractRequest();
-    });
+  Future<Response> _computeChange() async {
+    await _prepareOptions();
+    // send request with the options
+    return _sendExtractRequest();
   }
 
   Future<ExtractMethodFeedback> _computeInitialFeedback() {
     return waitForTasksFinished().then((_) {
       return _sendExtractRequest();
     }).then((Response response) {
       var result = new EditGetRefactoringResult.fromResponse(response);
       return result.feedback;
     });
   }
@@ skipping 1189 matching lines @@
     }
     fail('No SourceFileEdit for $testFile in $change');
   }
 
   @override
   Index createIndex() {
     return createMemoryIndex();
   }
 
   Future<EditGetRefactoringResult> getRefactoringResult(
-      Future<Response> requestSender()) {
-    return waitForTasksFinished().then((_) {
-      return requestSender().then((Response response) {
-        return new EditGetRefactoringResult.fromResponse(response);
-      });
-    });
+      Future<Response> requestSender()) async {
+    await waitForTasksFinished();
+    Response response = await requestSender();
+    return new EditGetRefactoringResult.fromResponse(response);
   }
 
   Future<Response> sendRequest(
       RefactoringKind kind, int offset, int length, RefactoringOptions options,
       [bool validateOnly = false]) {
     Request request = new EditGetRefactoringParams(
             kind, testFile, offset, length, validateOnly,
             options: options)
         .toRequest('0');
     return serverChannel.sendRequest(request);
@@ skipping 41 matching lines @@
         .toRequest('0');
     return _assertErrorResponseNoIndex(request);
   }
 
   _assertErrorResponseNoIndex(Request request) async {
     Response response = await serverChannel.sendRequest(request);
     expect(response.error, isNotNull);
     expect(response.error.code, RequestErrorCode.NO_INDEX_GENERATED);
   }
 }