[Optimization] Support for Target Independent Rasterization

[LifeIsStrange]

According to AMD, TIR can bring 500% higher performance in 2D vector graphics...
CF: https://softwareengineering.stackexchange.com/a/252600
This might be even more relevant than NV_PATH

Unclear to me wether this is the corresponding API
https://docs.microsoft.com/en-us/windows/win32/direct2d/what-s-new-in-direct2d-for-windows-8-consumer-preview#geometry-realizations

@nical @kvark

[nical]

That's specific to doing antialiasing for arbitrary path rendering which we don't support yet in WebRender. I don't think TIR is useful for the primitives that we implement at the moment.
It's in the long list of approach in consideration for future path rendering work (having shipped successfully in D2D). It's not universally available though.