Overflow list does not detect popover size correctly due to scale

[dylanrcooke]

Code Sandbox

Link to a minimal repro https://codesandbox.io/s/blueprint-sandbox-forked-xcw0jp?file=/src/index.tsx

Steps to reproduce

Use an overflow list in a popover with the minimal prop set to false

Actual behavior

The overflow list will never render more than one element

Expected behavior

The overflow list renders as many elements as fit in the container

Possible solution

• We currently scale the popover in css here
• If we switch to using element.offsetWidth instead of element.getBoundingClientRect().width it will remove the scale factor from the spacer repartition check.