[steveklabnik]

My understanding is that WebRender doesn't support everything yet, so right now it's mostly about validating correctness.

[infogulch]

Ah I see, so it basically enables a parallel run of webrender to gather compatibility/correctness stats.

[k__]

So it renders it two times and compares the results?

[Manishearth]

It renders it in series -- stuff goes through webrender first, and then whatever webrender couldn't handle gets dealt with with the regular renderer.