Description of problem:
Switching with Alt+Tab from Firefox makes file menu (with File, Edit, View... items) appear for a short time. Once I press and hold Alt+Tab, the menu appears and stays. When I release the combination (at least the tab), the application is switched and the menu is gone.

The issue doesn't appear with Super+Tab combination.


Version-Release number of selected component (if applicable):
Just updated the system.
Fedora 25 with GNOME (on Wayland) desktop
GNOME Shell 3.22.2
Firefox 50.0.2
I have installed "TopIcons Plus" and "No Topleft Hot Corner" gnome extensions. Also have Skype alpha for linux installed. Otherwise the system is pretty clean. 

How reproducible: 100%

Steps to Reproduce:
1. gsettings set org.gnome.desktop.wm.keybindings switch-applications "['<Super>Tab', '<Alt>Tab']"
2. Launch some application (say, gnome terminal) in a window mode (not maximized)
3. Launch firefox and maximize it
4. Press and hold Alt+Tab - notice the menu has appeared.
5. Release the Tab - notice the menu has dissapeared, and another application is active now.

Actual results:
The menu on Firefox appears during switch to another application.

Expected results:
The menu must not appear.

Additional info:
Isn't reproduced with Super+Tab