Inform window manager about modal windows in mus+ash.

services/ui/ws/test_utils.cc

Index: services/ui/ws/test_utils.cc
diff --git a/services/ui/ws/test_utils.cc b/services/ui/ws/test_utils.cc
index 94e8dbcdf008a2b6bed62508a7663499a84088c7..165c9a7344416c86dddf818ebadebb080bf62cb1 100644
--- a/services/ui/ws/test_utils.cc
+++ b/services/ui/ws/test_utils.cc
@@ -226,6 +226,10 @@ void TestWindowManager::WmDisplayRemoved(int64_t display_id) {
   display_removed_id_ = display_id;
 }
 
+void TestWindowManager::WmSetModalType(uint32_t window_id, ui::ModalType type) {
+  on_set_modal_type_called_ = true;
+}
+
 void TestWindowManager::WmCreateTopLevelWindow(
     uint32_t change_id,
     ClientSpecificId requesting_client_id,