Support creation of toplevel mus::Windows on separate displays

ash/mus/window_manager_unittest.cc

Index: ash/mus/window_manager_unittest.cc
diff --git a/ash/mus/window_manager_unittest.cc b/ash/mus/window_manager_unittest.cc
index 62a86dd139ee9f3db49fb7ca8a04f9547414e7d5..94b7f9e3ceb2ec79c50359b5b528595f5b6d9bd2 100644
--- a/ash/mus/window_manager_unittest.cc
+++ b/ash/mus/window_manager_unittest.cc
@@ -4,6 +4,7 @@
 
 #include <memory>
 
+#include "ash/mus/test/wm_test_base.h"
 #include "base/bind.h"
 #include "base/macros.h"
 #include "services/service_manager/public/cpp/service_test.h"
@@ -80,5 +81,26 @@ TEST_F(WindowManagerTest, MAYBE_OpenWindow) {
   ASSERT_TRUE(!child_client->GetRoots().empty());
 }
 
+using WindowManagerAshTest = mus::WmTestBase;
+
+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 mus
 }  // namespace ash