chromeos: makes WindowManager not delete shell when connection to mus is lost

ash/mus/window_manager.cc

 // Copyright 2015 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/window_manager.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 137 matching lines @@
   // client has been set.
   aura::client::CaptureClient* capture_client = wm_state_->capture_controller();
   pointer_watcher_event_router_->AttachToCaptureClient(capture_client);
   window_tree_client_->capture_synchronizer()->AttachToCaptureClient(
       capture_client);
 
   if (shell_delegate)
     shell_delegate_ = std::move(shell_delegate);
 }
 
+void WindowManager::SetLostConnectionCallback(base::OnceClosure closure) {
+  lost_connection_callback_ = std::move(closure);
+}
+
 bool WindowManager::WaitForInitialDisplays() {
   return window_manager_client_->WaitForInitialDisplays();
 }
 
 void WindowManager::DeleteAllRootWindowControllers() {
   // Primary RootWindowController must be destroyed last.
   RootWindowController* primary_root_window_controller =
       GetPrimaryRootWindowController();
   std::set<RootWindowController*> secondary_root_window_controllers;
   for (auto& root_window_controller_ptr : root_window_controllers_) {
@@ skipping 134 matching lines @@
 }
 
 void WindowManager::OnEmbedRootDestroyed(
     aura::WindowTreeHostMus* window_tree_host) {
   // WindowManager should never see this.
   NOTREACHED();
 }
 
 void WindowManager::OnLostConnection(aura::WindowTreeClient* client) {
   DCHECK_EQ(client, window_tree_client_.get());
+  if (!lost_connection_callback_.is_null()) {
+    base::ResetAndReturn(&lost_connection_callback_).Run();
+    return;
+  }
   Shutdown();
   // TODO(sky): this case should trigger shutting down WindowManagerApplication
   // too.
 }
 
 void WindowManager::OnPointerEventObserved(const ui::PointerEvent& event,
                                            aura::Window* target) {
   pointer_watcher_event_router_->OnPointerEventObserved(event, target);
 }
 
@@ skipping 238 matching lines @@
 bool WindowManager::IsWindowActive(aura::Window* window) {
   return Shell::Get()->activation_client()->GetActiveWindow() == window;
 }
 
 void WindowManager::OnWmDeactivateWindow(aura::Window* window) {
   Shell::Get()->activation_client()->DeactivateWindow(window);
 }
 
 }  // namespace mus
 }  // namespace ash