Make aura work with mus

ui/aura/test/env_test_helper.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_AURA_TEST_ENV_TEST_HELPER_H_
 #define UI_AURA_TEST_ENV_TEST_HELPER_H_
 
 #include <utility>
 
 #include "base/macros.h"
@@ skipping 11 matching lines @@
   void SetInputStateLookup(
       std::unique_ptr<InputStateLookup> input_state_lookup) {
     env_->input_state_lookup_ = std::move(input_state_lookup);
   }
 
   void ResetEventState() {
     env_->mouse_button_flags_ = 0;
     env_->is_touch_down_ = false;
   }
 
+  void SetWindowPortFactory(const Env::WindowPortFactory& factory) {
+    env_->window_port_factory_ = factory;
+  }
+
  private:
   Env* env_;
 
   DISALLOW_COPY_AND_ASSIGN(EnvTestHelper);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_ENV_TEST_HELPER_H_