The desktop shells resize the graphics context on the main thread, while drawing to it happens from a background thread. This can cause crashes (#17579), but even when it doesn't there are often strange rendering behaviors (red flashes, briefly transparent or garbage-filled windows, etc.)

Beyond just fixing the crashes, we need a robust solution to make resizing feel reasonable. Visually, synchronous repaints would probably be ideal, but something that isn't synchronous, but is highly responsive while avoiding shaking and/or tearing would likely feel good enough (c.f. Chromium's async renderer painting).