i will take this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d801b91bc31c10d43dafaaa41280140a1a72f2e4

commit d801b91bc31c10d43dafaaa41280140a1a72f2e4
Author: Hwanseung Lee <hs1217.lee@samsung.com>
Date: Mon May 14 21:22:37 2018

[WebUI] Update cr-action-menu hover background color

Focused item background color should be changed to
google-grey-200(#e8eaed).

Bug:  842380 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I9a16e764764fa1c908c5aeb0f523b5c9e88ea295
Reviewed-on: https://chromium-review.googlesource.com/1057648
Commit-Queue: Hwanseung Lee <hwanseung@chromium.org>
Reviewed-by: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558464}
[modify] https://crrev.com/d801b91bc31c10d43dafaaa41280140a1a72f2e4/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html
[modify] https://crrev.com/d801b91bc31c10d43dafaaa41280140a1a72f2e4/ui/webui/resources/cr_elements/shared_vars_css.html

hs1217.lee@ Request you to provide sample test file/steps to reproduce this issue, which will help us to verify the fix on the latest Canary 68.0.3431.0.

Thanks..

steps
1. chrome://downloads/ -> click menu (right top side) -> move mouse pointer to "Open downloads folder" -> observe background change when hover
2. chrome://bookmarks/ -> click menu (right top side) -> move mouse pointer to menu items -> observe background change when hover

thanks.