Thank you Prathmesh. --deep pulls in these packages:
11:11:59: NOTICE: These are the packages to emerge:
11:11:59: NOTICE: 1) dev-cpp/gtest-1.8.0
11:11:59: NOTICE: 2) chromeos-base/autotest-0.0.2-r8503
11:11:59: NOTICE: 3) chromeos-base/autotest-deps-0.0.4-r8516
11:11:59: NOTICE: 4) chromeos-base/metrics-0.0.1-r2290
11:11:59: NOTICE: 5) virtual/autotest-tests-3
11:11:59: NOTICE: * 6) chromeos-base/autotest-tests-9999
... and we achieve partial success! The error is now
emerge: there are no ebuilds to satisfy "chromeos-base/autotest-tests-cheets".
(dependency required by "virtual/autotest-tests-3::cheets-private" [binary])