bad interaction with test_injection.dart and stack_trace

[sigmundch]

The stack_strace package can't parse stack traces produced on these throws: https://github.com/angular/angular.dart/blob/master/lib/mock/test_injection.dart#L45 and https://github.com/angular/angular.dart/blob/master/lib/mock/test_injection.dart#L60

It seems that adding DECLARED AT is confusing the parsing in stack_trace, so you end up with an error like:

Uncaught FormatException: Couldn't parse V8 stack trace line 'DECLARED AT:at dart.wrapException

Not sure if the proper fix is here or there though.