"git cl upload" can take multiple minutes to execute, this is due to performing similarity checking on Chromium's enormous repository.
By passing in the --no-find-copies flag the time to upload can be reduced dramatically.

My guess is that most developers aren't aware of --no-find-copies and don't normally need this similarity checking either. Perhaps the default should be to --no-find-copies and a --find-copies flag be added for similarity checking.