Cleanup display creation in mus tests.

services/ui/ws/window_manager_state_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 "services/ui/ws/window_manager_state.h"
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 529 matching lines @@
   EXPECT_EQ("InputEvent window=1,1 event_action=7",
             ChangesToDescription1(*tracker->changes())[0]);
   WindowTreeTestApi(window_tree()).AckLastEvent(mojom::EventResult::UNHANDLED);
   EXPECT_FALSE(window_manager()->on_accelerator_called());
 }
 
 // Verifies there is no crash if the WindowTree of a window manager is destroyed
 // with no roots.
 TEST(WindowManagerStateShutdownTest, DestroyTreeBeforeDisplay) {
   WindowServerTestHelper ws_test_helper;
-  ws_test_helper.window_server_delegate()->CreateDisplays(1);
   WindowServer* window_server = ws_test_helper.window_server();
+  TestPlatformScreen platform_screen;
+  platform_screen.Init(window_server->display_manager());
+  platform_screen.AddDisplay();
   const UserId kUserId1 = "2";
   AddWindowManager(window_server, kUserId1);
   ASSERT_EQ(1u, window_server->display_manager()->displays().size());
   Display* display = *(window_server->display_manager()->displays().begin());
   WindowManagerDisplayRoot* window_manager_display_root =
       display->GetWindowManagerDisplayRootForUser(kUserId1);
   ASSERT_TRUE(window_manager_display_root);
   WindowTree* tree =
       window_manager_display_root->window_manager_state()->window_tree();
   ASSERT_EQ(1u, tree->roots().size());
   ClientWindowId root_client_id;
   ASSERT_TRUE(tree->IsWindowKnown(*(tree->roots().begin()), &root_client_id));
   EXPECT_TRUE(tree->DeleteWindow(root_client_id));
   window_server->DestroyTree(tree);
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace ui