Chrome Version : 73.0.3632.0 (Official Build) 914f5b8f721ff5a734bb22a96363191c20c8c3f2-refs/branch-heads/3632@{#1} 64-bit
OS : Mac(10.13.6, 10.13.1, 10.14.2)

What steps will reproduce the problem?
1. Launch chrome, open two NTPs and detach second NTP. (Kindly review an attached screencast)
2. Open 'Cast' overlay on second NTP and right click on 'Cast' icon (seen next to the omnibox) in first NTP.
3. Now hover mouse near 'Avatar' icon in detached NTP and observe.

Actual Result : Effect of mouse hover done on active detached NTP is seen on background tab.

Expected Result : Effect of mouse hover done on active detached NTP should not be seen on background tab.

This is a regression issue broken in M-70 and below is the bisect information:
Good Build : 70.0.3503.0 (Revision : 578160)
Bad Build : 70.0.3504.0 (Revision : 578510)

Change-Log URL:
https://chromium.googlesource.com/chromium/src/+log/bcb7db78edc13f57577f0a9562c98918bdcc10ae..67d21d10815fe6d87d1785a65a50fbc386e6605b

Suspect: https://chromium.googlesource.com/chromium/src/+/67d21d10815fe6d87d1785a65a50fbc386e6605b

@ellyjones: Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Note:
1. This is Mac OS specific issue and same isssue not reproducible in Windows(7,8,10) and Linux(14.04 LTS) OS
2. Issue is reproducible in Stable/Beta #71.0.3578.80 and Dev build #72.0.3626.7

Thank you..!
 

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