Fix undo edit step

Author: srujzs

dwds/test/hot_reload_test.dart

@@ -43,7 +43,8 @@ void main() {
   }
 
   void undoEdit() {
-    context.makeEditToDartEntryFile(
+    context.makeEditToDartLibFile(
+      libFileName: 'library1.dart',
       toReplace: newString,
       replaceWith: originalString,
     );
@@ -66,8 +67,8 @@ void main() {
     });
 
     tearDown(() async {
-      await context.tearDown();
       undoEdit();
+      await context.tearDown();
     });
 
     test('can hot reload', () async {

fixtures/_testHotReload/lib/library1.dart

@@ -2,4 +2,4 @@
 // 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.
 
-String get reloadValue => 'Bonjour le monde!';
+String get reloadValue => 'Hello World!';