From conversation in https://chromium-review.googlesource.com/c/chromium/src/+/754133

The fact that we need to copy & paste this flag multiple times mean the code here can be refactored to reduce boiler plate. I think there can be a single place that define the argparse for all flags of isolated-script-test. Then there is a based FlagsTransformer class that is the API for transforming each isolated script test flag to another flag supported by actual test frameworks (all base TransformXYZFlag methods will raise UnimplementedError). 

kbr@ raised a caution argument: 

"The underlying harnesses have completely different mechanisms for handling test filtering -- I counted something like 5 or 6 different mechanisms. I would caution against using too many abstractions in these trampoline scripts because they'll make the scripts harder to understand."