Remove SurfaceSequence from mus client code.

services/ui/public/cpp/window.cc

Index: services/ui/public/cpp/window.cc
diff --git a/services/ui/public/cpp/window.cc b/services/ui/public/cpp/window.cc
index 4368a2601a6915283920f80d4332922d429facc1..9deb327be21659f975b0df2ce77b233f410beb75 100644
--- a/services/ui/public/cpp/window.cc
+++ b/services/ui/public/cpp/window.cc
@@ -814,11 +814,7 @@ void Window::LocalSetSurfaceId(std::unique_ptr<SurfaceInfo> surface_info) {
         surface_info ? surface_info->surface_id : cc::SurfaceId();
     if (!existing_surface_id.is_null() &&
         existing_surface_id != new_surface_id) {
-      // Return the existing surface sequence.
-      if (client_) {
-        client_->OnWindowSurfaceDetached(server_id_,
-                                         surface_info_->surface_sequence);
-      }
+      // TODO(kylechar): Start return reference here?
     }
   }
   if (parent_ && parent_->surface_id_handler_) {