Inform window manager about modal windows in mus+ash.

services/ui/ws/test_utils.h

Index: services/ui/ws/test_utils.h
diff --git a/services/ui/ws/test_utils.h b/services/ui/ws/test_utils.h
index aa0c3ee55b1ac27b218a6a83fc1364190052fa52..c5c1be2c04c11da332fe9e526e96561f6a4a14ac 100644
--- a/services/ui/ws/test_utils.h
+++ b/services/ui/ws/test_utils.h
@@ -347,6 +347,9 @@ class TestWindowManager : public mojom::WindowManager {
       uint32_t window_id,
       const std::string& name,
       const base::Optional<std::vector<uint8_t>>& value) override {}
+  void WmSetModalType(uint32_t change_id,
+                      uint32_t window_id,
+                      ui::ModalType type) override {}
   void WmSetCanFocus(uint32_t window_id, bool can_focus) override {}
   void WmCreateTopLevelWindow(
       uint32_t change_id,