Make sure this uses the same logic as spinner.

There were fixes to determining the horizontal offset of the dropdown
view for spinners in fwk:
https://android-git.corp.google.com/g/#/c/128373/1

Since MultiAdapterSpinner doesn't use a spinner, we have to copy this logic.
Fixes b/5165079 account spinner dropdown padding / dropdown position off

Change-Id: Ifa0dfc319db65d36c6e0317cfbd10954e7ae16db