Makes display roots be destroyed by client

services/ui/test_wm/test_wm.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 <memory>
 #include <utility>
 
 #include "mojo/public/cpp/bindings/binding.h"
 #include "services/shell/public/c/main.h"
 #include "services/shell/public/cpp/connector.h"
@@ skipping 71 matching lines @@
     DCHECK(!root_);
     root_ = window;
     DCHECK(window_manager_client_);
     window_manager_client_->AddActivationParent(root_);
     ui::mojom::FrameDecorationValuesPtr frame_decoration_values =
         ui::mojom::FrameDecorationValues::New();
     frame_decoration_values->max_title_bar_button_width = 0;
     window_manager_client_->SetFrameDecorationValues(
         std::move(frame_decoration_values));
   }
+  void OnWmDisplayRemoved(ui::Window* window) override { window->Destroy(); }
   void OnWmPerformMoveLoop(Window* window,
                            mojom::MoveLoopSource source,
                            const gfx::Point& cursor_location,
                            const base::Callback<void(bool)>& on_done) override {
     // Don't care.
   }
   void OnWmCancelMoveLoop(Window* window) override {}
 
   ui::Window* root_ = nullptr;
   ui::WindowManagerClient* window_manager_client_ = nullptr;
   std::unique_ptr<ui::WindowTreeClient> window_tree_client_;
 
   DISALLOW_COPY_AND_ASSIGN(TestWM);
 };
 
 }  // namespace test
 }  // namespace ui
 
 MojoResult ServiceMain(MojoHandle service_request_handle) {
   shell::ServiceRunner runner(new ui::test::TestWM);
   return runner.Run(service_request_handle);
 }