Description
In the framework, we have several service extensions that are registered throughout the different bindings (example 'performanceOverlay' https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/widgets/binding.dart#L374).
These strings can easily be pulled out into constants so that they can be accessed by other libraries. DevTools stores a copy of each of these strings right now so that we can call the service extensions. This is not very robust because a name change or deletion could break our tooling. We should define the extension names as constants in the framework so that we can reference these names from Flutter in DevTools for more robustness and less copied code.