Telemetry doesn't meant to know about chromium directory (it lives in catapult/ which chromium/src/ depends on, no the other way around), so this find is part of the API that configure Telemetry to know where to look for certain files. 

Is the fact that this class is overridable concerns you?

Ah ok, it makes sense since Telemetry is agnostic to Chromium location.
It's alright to inherit ChromiumConfig from ProjectConfig. Thing still concerns me is that we pass a path to json in unspecified format. Better if ProjectConfig will provide methods like set_flash_plugin_path(), etc. It will exlicitly specify which features can be configured and which can't.
It's not time critical anyway.

I share your concern that none of the binaries set in the json file seems to be related to the code that use them in an obvious way.

I will leave this bug around for backlog purpose.

Thanks!