Make WindowTree::SetModal() take the type.

services/ui/public/interfaces/window_tree.mojom

Index: services/ui/public/interfaces/window_tree.mojom
diff --git a/services/ui/public/interfaces/window_tree.mojom b/services/ui/public/interfaces/window_tree.mojom
index ab53d13c0f7501385db27c8d9b40308e43bd897c..2c95a2e8bccf5353b3b0f31c0d2f4c35e3dd9ac0 100644
--- a/services/ui/public/interfaces/window_tree.mojom
+++ b/services/ui/public/interfaces/window_tree.mojom
@@ -12,6 +12,7 @@ import "services/ui/public/interfaces/mus_constants.mojom";
 import "services/ui/public/interfaces/window_manager.mojom";
 import "services/ui/public/interfaces/window_manager_constants.mojom";
 import "services/ui/public/interfaces/window_tree_constants.mojom";
+import "ui/base/mojo/ui_base_types.mojom";
 import "ui/events/mojo/event.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 import "ui/platform_window/mojo/text_input_state.mojom";
@@ -182,7 +183,7 @@ interface WindowTree {
   // This fails for any of the following reasons:
   // . |window_id| does not identify a valid window.
   // . Client does not have a valid user id (i.e., it is an embedded app).
-  SetModal(uint32 change_id, uint32 window_id);
+  SetModal(uint32 change_id, uint32 window_id, ModalType type);
 
   // Reorders a window in its parent, relative to |relative_window_id| according
   // to |direction|. Only the connection that created the window's parent can