Chrome Version : 71.0.3578.62 (Official Build) b1fa6dee27746dd62414ffad95ea3a7acf51ef16-refs/branch-heads/3578@{#760} 64-bit
OS : Mac(10.13.6, 10.13.1, 10.14.2)

What steps will reproduce the problem?
1. Launch chrome and open two NTPs.
2. Go to first NTP and drag/detach it and simultaneously observe the 'New tab (+)' icon in tab-strip. (Please review an attached screenshot)

Actual Result : 'New tab (+)' icon momentarily appears over the background tab's title while detaching an active tab.

Expected Result : 'New tab (+)' icon should not appear over background tab's title while detaching an active 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. Unable to reproduce issue in Linux(14.04 LTS) and Windows (7,8,8.1,10) OS.
2. Issue is reproducible in Stable #70.0.3538.110, Dev #72.0.3610.2 and Canary build #72.0.3616.0

Thank you..
 

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