The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/55484f7550ce62889190e5e51bc678bc8ef0f798

commit 55484f7550ce62889190e5e51bc678bc8ef0f798
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Tue Jul 31 17:15:27 2018

Enable confirm-to-quit on Mac by default

BUG= 869185 

Change-Id: I9785566ea733c97da198251f752b33a3a9a31e57
Reviewed-on: https://chromium-review.googlesource.com/1155811
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579445}
[modify] https://crrev.com/55484f7550ce62889190e5e51bc678bc8ef0f798/chrome/browser/ui/confirm_quit.cc

Able to reproduce the issue on Mac 10.12.6 on build without fix #70.0.3507.0.

Verified the fix on Mac 10.12.6, as per comment#0 on latest chrome version #70.0.3510.0.
Attaching screen shots for reference.
Observed that "Warn Before Quitting" is  default
Hence, the fix is working as expected.
Adding the verified labels.

Thanks...!!

Deleted: 70.0.3507.0.png 173 KB

	70.0.3507.0.png 173 KB View Download

Deleted: 70.0.3510.0.png 178 KB

	70.0.3510.0.png 178 KB View Download

 Issue 892222  has been merged into this issue.

FYI: User-Feedback regarding this change in  issue 896433 .