Able to reproduce the issue on mac 10.11 chrome version 53.0.2761.2 - Tab closes on middle mouse click with edit bookmark dialog box open.

This is also the case with Open/Save file dialogs. While left click is disabled, middle click for closing tabs works.

Trent, can you help triage this?

This has been around since forever, so it's probably not high priority. It would be good to fix it though.

Interestingly, it also happens in a full MacViews browser.

I guess I should take it - my CL in https://codereview.chromium.org/1354873002/ probably even fixes this already - that's for  Issue 528871 . But I don't think that CL will fix the views browser. Also I need to actually address Robert's review comment :p

This is also kinda the same as  Issue 29945  from 6.5 years ago. Chrome would crash back then - at least that doesn't happen any more.

 Issue 40809  is probably obsolete too. Also  Issue 65803  which is in Robert's queue. I wonder why all those ancient issues didn't get pinged by the Hotlist-Recharge goo.

 Issue 29945  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ceec40ad0ad238b6e37d1c18f478cee122b353b0

commit ceec40ad0ad238b6e37d1c18f478cee122b353b0
Author: tapted <tapted@chromium.org>
Date: Mon Jun 20 01:02:30 2016

Mac: Prevent mouse events reaching subviews while a window has an attached Sheet

It's currently possible to show a context menu for just about anything
in Chrome while the window has a modal sheet displayed (the exception is
the tab strip, which has a check in -[TabView menu]). This makes all
sorts of weird stuff possible, like showing a `Print` dialog for the
webcontents over the supposedly modal `Edit bookmark` dialog.

To fix, have the shared (and mostly boring) ancestor view, class
FastResizeView, override -[NSView hitTest:] to return itself when the
window has an attached sheet. This nerfs the context menus. (note: zoom
still works: that's handled by -[NSWindow sendEvent:] and seems to do
separate hit-testing when a sheet is displayed).

The TabStrip is in the titlebar, not a subview of FastResizeView, so it
also needs to check. This makes the check in -[TabView menu] obsolete.
We can't check "higher up" since the buttons in the window frame should
behave as before.

Note the mainMenu still functions as before. So a print dialog can still
be displayed. Just not via a context menu.

BUG= 528871 ,  617895 
TEST=Right-click the bookmarks toolbar and open a modal dialog (e.g.
Edit..., Add Page..., Add Folder...). Then:

- Right-clicking in the omnibox,tab strip or elsewhere shouldn't show a
context menu.
- Middle-clicking shouldn't close a tab.

Review-Url: https://codereview.chromium.org/1354873002
Cr-Commit-Position: refs/heads/master@{#400621}

[modify] https://crrev.com/ceec40ad0ad238b6e37d1c18f478cee122b353b0/chrome/browser/ui/cocoa/fast_resize_view.mm
[modify] https://crrev.com/ceec40ad0ad238b6e37d1c18f478cee122b353b0/chrome/browser/ui/cocoa/tabs/tab_strip_view.mm
[modify] https://crrev.com/ceec40ad0ad238b6e37d1c18f478cee122b353b0/chrome/browser/ui/cocoa/tabs/tab_view.mm