chromeos: makes it possible for windows to outlive WindowTreeClient

ash/shell_unittest.cc

 // Copyright (c) 2012 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.
 
 #include "ash/shell.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "ash/display/mouse_cursor_event_filter.h"
@@ skipping 488 matching lines @@
   ~ShellTest2() override {}
 
  protected:
   std::unique_ptr<aura::Window> window_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ShellTest2);
 };
 
 TEST_F(ShellTest2, DontCrashWhenWindowDeleted) {
-  // TODO: delete this test when conversion to mash is done. This test isn't
-  // applicable to mash as all windows must be destroyed before ash, that isn't
-  // the case with classic-ash where embedders can separately create
-  // aura::Windows.
-  if (Shell::GetAshConfig() == Config::MASH)
-    return;
-
   window_.reset(new aura::Window(NULL));
   window_->Init(ui::LAYER_NOT_DRAWN);
 }
 
 }  // namespace ash