With the following args.gn, isolated CrOS fails:

target_os = "chromeos"
is_debug = false
is_component_build = true
enable_nacl = false
use_goma = true

$ ninja -C out_cros/Release chrome browser_tests
$ python tools/swarming_client/isolate.py check -i out_cros/Release/browser_tests.isolate -s out_cros/Release/browser_tests.isolated
Failed to find an input file: /foo/src/out_cros/Release/chromevox_test_data/ is not a directory but ends with "/"
  -> returned 1
Execution failure: A .isolate file is required.

indeed, chromevox_test_data doesn't exist anywhere in out_cros/Release when building browser_tests with enable_nacl = false. This works with enable_nacl = true though.