Make use of "persist_mode" option in ScreenCast portal to restore previously selected screen/window and avoid picking it again in yet another xdg-desktop-portal dialog. Bug: webrtc:13429 Change-Id: I3a0068091c2dd38003a7dff3f82b9cdb2ccd0f42 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/263901 Commit-Queue: Jan Grulich <grulja@gmail.com> Reviewed-by: Alexander Cooper <alcooper@chromium.org> Cr-Commit-Position: refs/heads/main@{#37257}