Make WindowTree::SetModal() take the type.

services/ui/ws/server_window.h

Index: services/ui/ws/server_window.h
diff --git a/services/ui/ws/server_window.h b/services/ui/ws/server_window.h
index c600aa734013bc83c05e72c34cfa6bc0840da915..135c330a0791af1318029d3f83b4222715d96488 100644
--- a/services/ui/ws/server_window.h
+++ b/services/ui/ws/server_window.h
@@ -131,8 +131,8 @@ class ServerWindow {
 
   const Windows& transient_children() const { return transient_children_; }
 
-  bool is_modal() const { return is_modal_; }
-  void SetModal();
+  ModalType modal_type() const { return modal_type_; }
+  void SetModalType(ModalType modal_type);
 
   // Returns true if this contains |window| or is |window|.
   bool Contains(const ServerWindow* window) const;
@@ -237,7 +237,7 @@ class ServerWindow {
   ServerWindow* transient_parent_;
   Windows transient_children_;
 
-  bool is_modal_;
+  ModalType modal_type_;
   bool visible_;
   gfx::Rect bounds_;
   gfx::Insets client_area_;