Introduce window container to be used by lock screen app windows

ash/wm/event_client_impl.cc

Index: ash/wm/event_client_impl.cc
diff --git a/ash/wm/event_client_impl.cc b/ash/wm/event_client_impl.cc
index 7fbc2bf7361c3d00d4d5a288c1304d2b0c576aa5..c7f1e90c9cde178fbadc2821c07543bac03f3a81 100644
--- a/ash/wm/event_client_impl.cc
+++ b/ash/wm/event_client_impl.cc
@@ -7,6 +7,7 @@
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/session/session_controller.h"
 #include "ash/shell.h"
+#include "ash/tray_action/tray_action.h"
 #include "ui/aura/window.h"
 #include "ui/keyboard/keyboard_util.h"
 
@@ -32,11 +33,15 @@ bool EventClientImpl::CanProcessEventsWithinSubtree(
       root_window, kShellWindowId_LockScreenWallpaperContainer);
   const aura::Window* lock_screen_related_containers = Shell::GetContainer(
       root_window, kShellWindowId_LockScreenRelatedContainersContainer);
+  const aura::Window* lock_action_handler_container = Shell::GetContainer(
+      root_window, kShellWindowId_LockActionHandlerContainer);
   bool can_process_events =
       (window->Contains(lock_screen_containers) &&
        window->Contains(lock_wallpaper_containers) &&
        window->Contains(lock_screen_related_containers)) ||
-      lock_screen_containers->Contains(window) ||
+      (lock_screen_containers->Contains(window) &&
+       (!lock_action_handler_container->Contains(window) ||
+        Shell::Get()->tray_action()->IsLockScreenNoteActive())) ||
       lock_wallpaper_containers->Contains(window) ||
       lock_screen_related_containers->Contains(window);
   if (keyboard::IsKeyboardEnabled()) {