Bug 185677 – drop-shadow filter prevents div background refresh with overflow: auto

• Status: NEW
• Component: Layout and Rendering

[Tatiana]

We have div contains items with drop-shadow filter and these items are under initially visible area. When scrolling down we can see that background is not updating.

Steps to reproduce:
1) Open https://codepen.io/tbelousova/pen/bMmNaq in Safari
2) Click on the visible item of the left list. These items have drop-shadow filter. Item will change background to red.Text of the clicked div will be shown between lists.
3) Scroll down this list and click previously invisible item. Background either won't be changed or there will be drawing artifacts. Text of the clicked div will be shown between lists.
4) If rotate device background will be rendered. After first not-rendered background other items' backgrounds can be not rendered as well.
5) Click on the visible item of the right list. These items don't have drop-shadow filter. Item will change background to blue. Text of the clicked div will be shown between lists.
6) Scroll down this list and click previously invisible item. Item will change background to blue. Text of the clicked div will be shown between lists.

So list without drop-shadow is rendered correctly while with drop-shadow not.

Tested on iPad3 with IOS 8.4, iPhone5 IOS 10.3.3, iPhone 5S iOS 11.3, iPhone 10 iOS 11.3

[Radar WebKit Bug Importer]

<rdar://problem/40650855>