This problem may not be a bug from the wikimedia, but report it because it happened here.
Steps to Reproduce:
Open like https://gerrit.wikimedia.org/r/admin/repos/pywikibot/core,commands, click the Create change.
Try to clicking or type in the "Select branch for new change" input box.
Actual Results:
There is no drop-down list or auto-complete. This is the trouble to enter or copy the branch name.
Expected Results:
Drop-down list, auto-complete, prefill the default branch name.