Fix 'Followup on earlier review: Cleans up treatment..'
Fix 'Followup on earlier review: Cleans up treatment..'

The last-minute argument name rename operation in said commit was
incomplete, which made every test fail. This CL completes that rename
operation, and it passes tests.

R=sigurdm@google.com

Review URL: https://codereview.chromium.org/1417493002 .

google/reflectable.dart,google/reflectable.dart