GYP build will stop supporting IBus client. · Issue #567 · google/mozc
https://github.com/google/mozc/issues/567

・ Gtk2 based candidate window for IBus will be removed.
Qt based candidate window is the alternative.

・ GYP build will stop supporting the build of IBus client.
Bazel build is the alternative.

・ Then, pull requests for IBus client and Qt based candidate window will be acceptable.