Enable dropdown_test

Author: elliette

…rarily_disabled_tests/dropdown_test.dart …ages/material_ui/test/dropdown_test.dartpackages/material_ui/temporarily_disabled_tests/dropdown_test.dart renamed to packages/material_ui/test/dropdown_test.dart packages/material_ui/temporarily_disabled_tests/dropdown_test.dart renamed to packages/material_ui/test/dropdown_test.dart

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-@Skip(
-  'This file is skipped due to a cross-import that needs to be fixed. Tracked in https://github.com/flutter/flutter/issues/177028.',
-)
 // no-shuffle:
 //   //TODO(gspencergoog): Remove this tag once this test's state leaks/test
 //   dependencies have been fixed.
@@ -21,13 +18,13 @@ import 'dart:ui';
 
 import 'package:cupertino_ui/cupertino_ui.dart';
 import 'package:flutter/foundation.dart';
-import 'package:material_ui/material_ui.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_ui/material_ui.dart';
 
-import '../widgets/feedback_tester.dart';
-import '../widgets/semantics_tester.dart';
+import 'feedback_tester.dart';
+import 'semantics_tester.dart';
 
 const List<String> menuItems = <String>['one', 'two', 'three', 'four'];