Poor performance following ShadowAssist.CacheMode change #3616

まだ誰も着手していません。

### Bug explanation

It seems that specifically following commit #3616 to change the default ShadowAssist CacheMode behaviour, I find the performance of our WPF app to be a lot slower and laggy than it was before, particularly when it comes to animations such as those in the DialogHost flyouts. It's particularly bad after resizing the window or in full screen.

I'm trying to figure out the best way to replicate the old behaviour. I've tried to set a `CacheMode `with `EnableClearType` and `SnapsToDevicePixels` but it seems like I have to set this all the way down and just setting it on the window or main containing control doesn't work.

Would appreciate any guidance on this. Has anyone else had a similar problem or know the best way to handle the CacheMode property globally? Is that even the right approach or should it only be set for troublesome controls?

### Version

5.2.1

まず commit #3616 を確認し、WPF アプリで発生する速度低下を再現します。ウィンドウのサイズ変更後またはフルスクリーンへの移行後の DialogHost flyout アニメーションに重点を置いてください。CacheMode の動作を以前のバージョンと比較し、問題が全体に及ぶのか、問題のあるコントロールに限定されるのかを判断します。再現可能な原因と、文書化された対処方法が確立されれば完了です。

索引モデルが issue の本文から書いたものです。