GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
cf. discussion in #18861 (moved); summary:
Considering the plans about the new file structure (cf. #18964 (moved)) I'd suggest test/java in package org.torproject.descriptor.benchmark.
It will be excluded from javadoc and unit tests.
Maybe, add a new ant task benchmark?