Version: 55.0.2842.0 d49de86acc4a6b7382a2fff2a7d9939673df3b76-refs/heads/master@{#414942} (64-bit)
OS: Windows (7,8,8.1,10),Linux (14.04 LTS),Mac OS X(10.10.5, 10.11.4)

What steps will reproduce the problem?
1. Launch chrome and navigate to chrome://md-settings/advanced
2. Now open 'Languages' and click on 'More actions' icon to open options drop down lists besides 'English' language. 
3. Now press 'Tab' key from keyboard to move focus to 'Remove' button and the press 'Shift' + 'Tab' key to move focus in reverse direction,observe

Actual: Focus does not move to 'Language settings' option on pressing 'Shift' + 'Tab' key
Expected: Focus should move to 'Language settings' option on pressing 'Shift' + 'Tab' key

This is regression issue, broken in ‘M 55’ and below is manual regression and narrow bisect info:
Good build : 55.0.2841.0
Bad build : 55.0.2842.0

Narrow Bisect info : 
https://chromium.googlesource.com/chromium/src/+log/f05e88ae004f438fcd8fb2023b51ba19a7903e48..3767fa543bcbdef5c254599a9d4d6833de4e44df?pretty=fuller&n=1000

Suspecting: r414891 from Narrow bisect

@michaelpg : Could you please help to reassign if your change is not the cause for this change.
 

Deleted: Actual_video.mov 5.3 MB

Actual_video.mov 5.3 MB Download

Deleted: Expected_video.mov 3.3 MB

Expected_video.mov 3.3 MB Download