Reproduction

https://stackblitz.com/edit/angular-v8fc5s-kitja5

Steps to reproduce:
Take first element and scroll with it to the bottom of page (you can drag past drag boundry) then (without dropping) try to scroll with this element to the top of page
This is similar to #18597

Expected Behavior

What behavior were you expecting to see?
Dragged element should be constrained by boundary element

Actual Behavior

What behavior did you actually see?
Boundary is not recalculated after scroll

Environment

• Angular: 9.1.0
• CDK/Material: 9.2.1
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): macOS

Is there any workaround for this problem? I tried to provide DragDrop with ViewportRuler that uses dialog container as document, with this setup boundary is correct but placeholder position is wrong