Chrome Version: 62.0.3202.43/9901.35.0 Dev-channel  Kip, Celes & Peppy
OS: Chrome

What steps will reproduce the problem?
(1)Sign in to user >> Sign out >> In Sign-Out Screen Press 'Tab' Button
(2)Observe Focus traversal and when it reaches the dropdown near user id, Hit enter
(3)Again Tab

Expected: Focus should be on shut down button 
Actual: Focus is seen on ubertray.

NOTE: Issue is also seen on Lock screen
      Issue is also seen in latest M-63

@wzang: Please confirm the issue

This is non-regression issue seen from M55.

Attaching screen-cast for reference.
 

Deleted: FocusSignout.mp4 4.4 MB

	FocusSignout.mp4 4.4 MB View Download