UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.52 Safari/537.36

Steps to reproduce the problem:
Sometimes when I'm using Chrome, I decide to scroll with the arrow keys instead of my mouse. And sometimes, instead of scrolling the page, the arrow keys trigger a menu item to appear at the top of my screen. As if an offscreen menu button had focus instead of the page, and pressing down opened it for some reason. When the menu item first appears, it has a grey background. If I hit up or down again while it's open, the its background becomes blue as if it's highlighted. Pressing up or down again does not change it, implying that it's the only menu item. Clicking it doesn't seem to do anything.

I've attached a screenshot of it while it's in the highlighted state. (I've censored unrelated parts of my screen.) Maybe someone can recognize the menu item widget from its appearance? It doesn't look like any standard macOS menu item or notification.

The text on the menu item is always "dtrt-indent", which is the name of an emacs plugin that I once cloned the git repo of back in 2014. I haven't used emacs in a long time, I haven't interacted with that directory or its files in years, emacs and this plugin don't have anything to do with menus like that, and the issue only happens when Chrome is focused (note that the Mac menu at the top left in the screenshot says "Chrome", naming it as the active window), so I'm not convinced this has anything to do with the dtrt-indent plugin itself. I think Chrome is just showing the name of a specific random file from my computer. I've renamed it, so if I run into the issue again I can see if the menu item has a new name now.

I can't reliably reproduce the issue. Usually the issue happens on the first arrow key press after I use my mouse to switch focus from another application's window to Chrome. When the issue happens it, I can repeat it dependably: I can click a different window, the menu item goes away, I click chrome, press an arrow key, the menu item comes back. If I click the chrome window multiple times (to actually focus the web page?) and then press an arrow key, then the issue stops happening.

I have some chrome extensions active right now: (in order of display at the top right) chromecast, extensions reloader, a super-simple private extension that only modifies a site I don't have open at the time of this screenshot, adblock plus, and reload css. None of these extensions should have access to my filesystem, be able to create a menu item like this, or steal focus while I'm on random web pages like this, so I don't think any of them are related.

What is the expected behavior?
Pressing the down arrow should scroll down the page, or do whatever action down arrow is supposed to do for whatever has focus.

What went wrong?
A weird menu item appears on my screen.

Did this work before? N/A 

Chrome version: 62.0.3202.52  Channel: beta
OS Version: OS X 10.11.6
Flash Version: 

Take a look at the screenshot and see if you recognize the menu item widget at least.
 

Deleted: Screen Shot 2017-10-13 at 11.00.12 AM.png 1.6 MB

	Screen Shot 2017-10-13 at 11.00.12 AM.png 1.6 MB View Download