onscreen/native: Avoid freezing the frame clock on failed cursor commits

Since 73fb64cbb6 we have preferred to handle failed updates via callback
but the cursor-only update path was forgotten and so wasn't getting frame
notifications. And so the frame clock would freeze.

Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2691
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2933>

src/backends/native/meta-onscreen-native.c

@@ -1525,6 +1525,29 @@ meta_onscreen_native_prepare_frame (CoglOnscreen *onscreen,
     }
 }
 
+static void
+on_finish_frame_update_result (const MetaKmsFeedback *kms_feedback,
+                               gpointer               user_data)
+{
+  CoglOnscreen *onscreen = COGL_ONSCREEN (user_data);
+  const GError *error;
+  CoglFrameInfo *frame_info;
+
+  error = meta_kms_feedback_get_error (kms_feedback);
+  if (!error)
+    return;
+
+  if (!g_error_matches (error,
+                        G_IO_ERROR,
+                        G_IO_ERROR_PERMISSION_DENIED))
+    g_warning ("Cursor update failed: %s", error->message);
+
+  frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
+  frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
+
+  meta_onscreen_native_notify_frame_complete (onscreen);
+}
+
 void
 meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
                                    ClutterFrame *frame)
@@ -1544,6 +1567,10 @@ meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
       return;
     }
 
+  meta_kms_update_add_result_listener (kms_update,
+                                       on_finish_frame_update_result,
+                                       onscreen_native);
+
   meta_kms_update_add_page_flip_listener (kms_update,
                                           kms_crtc,
                                           &page_flip_listener_vtable,