Bisection is:

You are probably looking for a change made after 479805 (known good), but no later than 479818 (first known bad).

Robert's change is https://chromium-review.googlesource.com/c/536513 , r479808. Assigning to him.

Ah, the difference is that I only blocked right-click, not click-hold.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/36969c47fb5943856ceb8e76dbc65c7df662f0b5

commit 36969c47fb5943856ceb8e76dbc65c7df662f0b5
Author: Robert Sesek <rsesek@chromium.org>
Date: Thu Jul 06 18:34:23 2017

[Mac] Do not open the reload button menu on click-hold unless DevTools is open.

After f7fd12c1dedd498830bc2e9d049687749dbadcf9, the menu could be opened by
click-hold-drag even if DevTools were not open, due to the way MenuButton
works. The menu should only be avaiable if DevTools is open.

This CL adds a new openMenuOnClickHold property to MenuButton, defaulting
to YES, that can be used to disable the click-hold-drag behavior of the
button. This is now set for the reload button.

In addition, this fixes, enables, and expands MenuButtonTest.OpenOnClickAndHold.

Bug:  739467 
Bug:  517384 
Change-Id: I70d900964734dd5c30f2d97fdfdaa32cd4551544
Reviewed-on: https://chromium-review.googlesource.com/562116
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484685}
[modify] https://crrev.com/36969c47fb5943856ceb8e76dbc65c7df662f0b5/chrome/browser/ui/cocoa/menu_button.h
[modify] https://crrev.com/36969c47fb5943856ceb8e76dbc65c7df662f0b5/chrome/browser/ui/cocoa/menu_button.mm
[modify] https://crrev.com/36969c47fb5943856ceb8e76dbc65c7df662f0b5/chrome/browser/ui/cocoa/menu_button_unittest.mm
[modify] https://crrev.com/36969c47fb5943856ceb8e76dbc65c7df662f0b5/chrome/browser/ui/cocoa/toolbar/reload_button_cocoa.mm

Tested the issue on Mac OS X 10.12.5 using Chrome Dev# 61.0.3153.4 and noticed that the functionality is working as intended.
Below are the steps followed --
(i) Launched Chrome and opened Dev Tools.
(ii) Click and hold reload button to observe context menu.

Attaching a screenshot for reference. Adding TE-Verified labels accordingly.

Thank You.

Deleted: 739467.png 193 KB

	739467.png 193 KB View Download