Most notably, the fact that layer-backed views always draw on top of non-layer-backed views, and that this ignores |GetChildrenInZOrder| can lead to issues like
https://bugs.chromium.org/p/chromium/issues/detail?id=846900#c5

I conjecture that this also affects event targeting (see https://bugs.chromium.org/p/chromium/issues/detail?id=842064) and other stuff that we either don't know about or is not widely known among views toolkit users.