[Bug 57072] Window is flashing when painting transluent effects

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=57072

--- Comment #4 from Zeb Figura  ---
The application is constantly rendering to two different swapchains on two
different windows. wined3d keeps track of whether it has set the internal pixel
format on a swapchain, but that's a per-context flag and when the context
switches windows it needs to be invalidated.

We should avoid redundantly setting the pixel format, or at least recreating
the GL drawable when the pixel format is set redundantly. I'm not sure that
explains why flickering happens though; I'd only expect it to have performance
implications?