how to disable dart:mirrors warning messages during test compilation for chrome?

I'm using dart:mirrors in my project because I need reflection capabilities. Since mirrors are experimental, I was receiving the usual warning telling me that.
I've been able to disable these warnings during a pub build by adding the transformer:

- $dart2js:
    commandLineOptions: [--enable-experimental-mirrors]

to my pubspec.yaml, however, since I need to test the build on chrome, I still receive the warning message when I execute the test command

pub run test -p chrome  

Apparently the build triggered by pub run test is ignoring my pubspec. Is there a way to eliminate the wranings even on the test? is it a bug?