Windows: High-DPI mode causes black banding and incorrect mouse positioning

To reproduce:

1. Open Windows Display settings
2. Set scale to 125% (or presumably anything > 100%)
3. Run the sample app

Observe that the entire UI is offset towards the bottom right, leaving a black band in the missing space, as well as incorrect mousing behavior.

Seems related to https://github.com/cefsharp/CefSharp/issues/1757.