Chrome Version:  63.0.3239.116/ 10032.75.0  stable-channel Daisy,Reks and Candy
OS: Chrome

What steps will reproduce the problem?
(1)Sign in to user -> Go to chrome://settings
(2)Now at 'People' section select 'Manage other people' option which navigates to 'Manage Other users' page -> Enable  'Restrict sign-in to the following users' option so that 'Add person' option is enabled
(3)Now click on 'Add person' -> Add users until scrollbar is seen -> Now scroll up
(4)Disable 'Restrict sign-in to the following users' option -> now scroll and observe for scrollbar (Please refer Video)

Expected: Scrollbar should be seen on scrolling at 'Restrict sign-in to the following users'
Actual: Instead Scrollbar is seen missing

This is Regression Issue as same is working fine in old settings page i.e. Scrollbar is seen 

@stevenjb: Please confirm the Issue

Note: Issue is seen on M-65 also
 

Deleted: Actual_NoScrollbar.webm 1.8 MB

	Actual_NoScrollbar.webm 1.8 MB View Download

Deleted: Expected_Scrollbar.webm 1.3 MB

	Expected_Scrollbar.webm 1.3 MB View Download