Edge dialog

I was testing a sketch on the web editor using Windows Edge web browser. I had been re-writing a sketch, but forgot to save my work before disconnecting the USB cable. I was just looking at the screen trying to decide if I should close the editor page, or leave it until later -probably tomorrow. A message popped up asking if I wanted to leave this page before saving. I decided to save my sketch changes. Is that an Edge feature, or Arduino? This is not a problem, so, I didn't follow the Edge issue link.

The message is not specific to EDGE and will appear if changes have been made to a sketch but not saved.

It could be a little more descriptive I think.

I also get it here on win 7 with Chrome or Firefox.

The message popping up comes from your browser, if you are writing an email and leave it without saving a similar message will be displayed.

The Edge browser I am using is new to me. It is quite a bit different from Windows web browsers of yore. I'm not even sure Windows Internet Explorer is loaded on this device. I don't want it.
I have been using Chrome on my desktop exclusively for the last 7 years. By now, it has been customized with ad blockers and pop-up blockers, and the latest thing that just appeared is a McAfee extension for rating website risk.
So, it may well have been an anti-popup extension that has blocked the save page dialog before now.
My plan is to use Edge exclusively with Arduino web editor. My Chrome browser has so many bookmarks and, like I said, forgotten extensions and what-not, that a second web browser will be nice.