mus: Changes SetDisplayRoot() to create actual display

services/ui/ws/test_utils.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/test_utils.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "cc/output/copy_output_request.h"
@@ skipping 124 matching lines @@
 void TestScreenManager::Init(display::ScreenManagerDelegate* delegate) {
   delegate_ = delegate;
 
   // Reset everything.
   display_ids_.clear();
   display::Screen::SetScreenInstance(nullptr);
   screen_ = base::MakeUnique<display::ScreenBase>();
   display::Screen::SetScreenInstance(screen_.get());
 }
 
+display::ScreenBase* TestScreenManager::GetScreen() {
+  return screen_.get();
+}
+
 // TestPlatformDisplayFactory  -------------------------------------------------
 
 TestPlatformDisplayFactory::TestPlatformDisplayFactory(
     mojom::CursorType* cursor_storage)
     : cursor_storage_(cursor_storage) {}
 
 TestPlatformDisplayFactory::~TestPlatformDisplayFactory() {}
 
 std::unique_ptr<PlatformDisplay>
 TestPlatformDisplayFactory::CreatePlatformDisplay(
@@ skipping 531 matching lines @@
   if (!tree->AddWindow(parent_client_id, client_window_id))
     return nullptr;
   if (client_id)
     *client_id = client_window_id;
   return tree->GetWindowByClientId(client_window_id);
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace ui