You can use the `--user-data-dir` arg to specify a profile location when opening chrome. So, on a mac, something like:

  open -Fna /Applications/Google\ Chrome.app \
  --args --user-data-dir=/my_temp_profile_dir/my_tmp_profile

If you copy an existing profile to `my_tmp_profile` chrome will use that, otherwise it behaves like a new setup.