Remove making added files as changed.

pkg/analyzer/test/src/dart/analysis/driver_test.dart

 // Copyright (c) 2016, 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 analyzer.test.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 284 matching lines @@
         r'''
 import 'a.dart';
 main() {
   print(A);
 }
 ''');
     driver.changeFile(b);
     await _waitForIdle();
     assertNumberOfErrorsInB(0);
 
-    // Change 'b' t have a hint again.
-    // Add and remove 'b'.
-    // The file must be refreshed, and the hint must be reported.
+    // Change 'b' content so that it has a hint.
+    // Remove 'b' and add it again.
+    // The file 'b' must be refreshed, and the hint must be reported.
     provider.newFile(
         b,
         r'''
 import 'a.dart';
 ''');
     driver.removeFile(b);
     driver.addFile(b);
     await _waitForIdle();
     assertNumberOfErrorsInB(1);
   }
@@ skipping 1209 matching lines @@
   String _p(String path) => provider.convertPath(path);
 
   Future<Null> _waitForIdle() async {
     await idleStatusMonitor.signal;
   }
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }