mash: Fix crash when closing system tray menu

ash/mus/wm/container_finder_unittest.cc

+// Copyright 2016 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/common/wm/container_finder.h"
+
+#include "ash/common/shell_window_ids.h"
+#include "ash/common/wm_window.h"
+#include "ash/mus/bridge/wm_window_mus.h"
+#include "ash/mus/test/wm_test_base.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace ash {
+
+using ContainerFinderTest = mus::WmTestBase;

[James Cook, 2016/08/26 17:49:13]

I did the same thing as MruWindowTrackerTest and created versions for aura and
mus, since the tests need different base classes.

+
+TEST_F(ContainerFinderTest, GetContainerForWindow) {
+  // Create a normal window in the default container.
+  WmWindow* window =
+      mus::WmWindowMus::Get(CreateTestWindow(gfx::Rect(1, 2, 3, 4)));
+
+  // The window itself is not a container.
+  EXPECT_EQ(kShellWindowId_Invalid, window->GetShellWindowId());
+
+  // Container lookup finds the default container.
+  WmWindow* container = wm::GetContainerForWindow(window);
+  ASSERT_TRUE(container);
+  EXPECT_EQ(kShellWindowId_DefaultContainer, container->GetShellWindowId());
+}
+
+}  // namespace ash