arc: Implement proper Arc window activation for task moving to front.

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 497a50e9cfaff4db00e99b6d34b7d475544d6b06..550dbdbd3b3704106b85881f41f3e7051d529fb9 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
@@ -463,6 +463,16 @@ void ArcAppWindowLauncherController::OnTaskSetActive(int32_t task_id) {
   }
 }
 
+void ArcAppWindowLauncherController::OnTaskMovedToFront(int32_t task_id) {
+  TaskIdToAppWindow::const_iterator app_it =
+      task_id_to_app_window_.find(task_id);
+  if (app_it == task_id_to_app_window_.end())
+    return;
+  if (app_it->second->IsActive())
+    return;
+  app_it->second->Activate();
+}
+
 void ArcAppWindowLauncherController::OnTaskOrientationLockRequested(
     int32_t task_id,
     const arc::mojom::OrientationLock orientation_lock) {