[Merge M58] arc: Fix regression in handling ARC shelf item.

chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc

Index: chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
diff --git a/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc b/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
index bf4b2022b740868c18438c3e42eed859474c3ae2..a905936c2d90dc869d6301708a7de8c58ee445c1 100644
--- a/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
@@ -568,6 +568,9 @@ void ArcAppWindowLauncherController::OnTaskOrientationLockRequested(
 
 AppWindowLauncherItemController*
 ArcAppWindowLauncherController::ControllerForWindow(aura::Window* window) {
+  if (!window)
+    return nullptr;
+
   AppWindow* app_window = GetAppWindowForTask(active_task_id_);
   if (app_window &&
       app_window->widget() == views::Widget::GetWidgetForNativeWindow(window)) {
@@ -590,6 +593,8 @@ void ArcAppWindowLauncherController::OnWindowActivated(
     aura::client::ActivationChangeObserver::ActivationReason reason,
     aura::Window* gained_active,
     aura::Window* lost_active) {
+  AppWindowLauncherController::OnWindowActivated(reason, gained_active,
+                                                 lost_active);
   OnTaskSetActive(active_task_id_);
 }