r615326 seems to be the culprit.

Could you let me know the flags and page you're using to test this?

https://rsolomakhin.github.io/autofill/

Right click on the password field and click "Suggest password". You need to be signed-in to Chromium.

 Issue 916466  has been merged into this issue.

I don't see the Suggest Password option. Are there flags/settings that affect whether or not it appears?

Are you signed-in to Chrome and syncing passwords?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5d56c7995b20069d803d3a1f54f0323fe7d255ef

commit 5d56c7995b20069d803d3a1f54f0323fe7d255ef
Author: tmartino <tmartino@chromium.org>
Date: Thu Jan 10 16:24:23 2019

Fixing Password Generation transparency issue

This CL fixes a small issue where the divider between the content and
footer of the Password Generation popup is transparent on macOS. It
adds a call to set a white background behind the popup, which is
consistent with what we do in AutofillPopupViewNativeViews.

Bug:  913968 
Change-Id: I113477fd3b6bcd621540f83c476f51669d403453
Reviewed-on: https://chromium-review.googlesource.com/c/1403939
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621593}
[modify] https://crrev.com/5d56c7995b20069d803d3a1f54f0323fe7d255ef/chrome/browser/ui/views/passwords/password_generation_popup_view_views.cc

This should be fixed. Could one of Max or Vasilii please verify in tomorrow's Canary that everything looks the way they expect it?

Update:

Rechecked the above issue on  Mac(10.13.1, 10.13.6, 10.14.3) OS using latest Canary build #73.0.3668.0 and the issue is fixed. Kindly refer attached screen cast.

Thank you

Deleted: Fixed Result.mov 1.1 MB

	Fixed Result.mov 1.1 MB View Download