Chrome Version: 67.0.3396.49/ 10575.40.0 beta-channel Daisy,Candy,Reks 
OS:Chrome OS

What steps will reproduce the problem?
(1)Sign into user >> Open NTP >> Keep it in Overview mode and observe its header border

Actual: Header border is seen transparent without any highlight
Expected: Header border should be seen highlighted 

This is a Regression issue seen as same is working fine in 66.0.3359.181/10452.96.0 Stable

Note: Issue is not seen in Linux,Windows OS

Attached the screenshots for reference..
 

Deleted: Actual.jpg 3.8 MB

	Actual.jpg 3.8 MB View Download

Deleted: Expected.jpg 3.4 MB

	Expected.jpg 3.4 MB View Download