Support creation of toplevel mus::Windows on separate displays

ash/mus/window_manager_ash_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/mus/test/wm_test_base.h"
+#include "base/bind.h"
+#include "base/macros.h"
+#include "services/ui/public/cpp/window.h"
+
+namespace ash {
+class WindowManagerAshTest : public mus::WmTestBase {

[mfomitchev, 2016/11/18 17:36:24]

No reason to create a new class if you are not overriding any behavior.  YOu can
do 
using WindowManagerAshTes = mus::WmTestBase;
if you wish.

[thanhph, 2016/11/18 19:15:44]

Cool, thanks..I updated the code to this!

+ public:
+  WindowManagerAshTest() {}
+  void SetUp() override { mus::WmTestBase::SetUp(); }
+  ~WindowManagerAshTest() override {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WindowManagerAshTest);
+};
+
+TEST_F(WindowManagerAshTest, isWidgetShownInCorrectDisplay) {
+  if (!SupportsMultipleDisplays())
+    return;
+
+  UpdateDisplay("400x400,400x400");
+  EXPECT_NE(GetPrimaryRootWindowController(),
+            GetSecondaryRootWindowController());
+
+  ui::Window* ui_primary_window =
+      CreateFullscreenTestWindow(GetPrimaryRootWindowController());
+  ui::Window* ui_secondary_window =
+      CreateFullscreenTestWindow(GetSecondaryRootWindowController());
+
+  DCHECK(ui_primary_window);
+  DCHECK(ui_secondary_window);
+
+  EXPECT_NE(ui_primary_window->display_id(), ui_secondary_window->display_id());
+}
+
+}  // namespace ash