For bugs in Firefox Desktop, the Mozilla Foundation's web browser. For Firefox user interface issues in menus, developer tools, bookmarks, location bar, and preferences. Many Firefox bugs will either be filed here or in the Core product. (more info)
1. Put gmail as an app tab and select it
2. Use mac-shift-[ or mac-shift-]
Result: gmail icon blinks
It doesn't seem to happen for other app tabs, and if it happens when I click the tab, it is less obvious.