Due to:

https://searchfox.org/mozilla-central/rev/1843375acbbca68127713e402be222350ac99301/gfx/webrender_bindings/RenderCompositorANGLE.cpp#136

We have a race condition where device reset handling might not complete before a new window is created. This happens in the wild. As a result, the window creation fails, and we disable WebRender.

We don't clear the flag until the last RenderCompositor is destroyed:

https://searchfox.org/mozilla-central/rev/1843375acbbca68127713e402be222350ac99301/gfx/webrender_bindings/RenderThread.cpp#227

This also blocks us recreating the SharedGL context, presumably because we don't want to destroy it until all of the RenderCompositors depending on it are destroyed:

https://searchfox.org/mozilla-central/rev/1843375acbbca68127713e402be222350ac99301/gfx/webrender_bindings/RenderCompositorANGLE.cpp#130

We should handle this race condition. We also need to ensure the SharedGL clearing is available on other platforms as well -- both Linux/Wayland and Android use a shared EGL context, although at the moment, we don't have robustness enabled on either of those configuration.