+1, I've seen this in a number of places and the truth is that you actually never need to check `node.classList.contains(class)` if all you need to do is add or remove:

1. `node.classList.add()` will not allow a duplicate, so if the class already exists, the duplicate will be ignored.
2. `node.classList.remove()` will silently ignore code that attempts to remove a class that doesn't exist. 

Spotted in:

- gaia/apps/communications/ftu/js/navigation.js
- gaia/apps/gallery/js/complete.js
- gaia/apps/gallery/js/frame_scripts.js
- gaia/apps/gallery/js/frames.js
- gaia/apps/system/js/window_manager.js
- gaia/apps/system/js/wrapper.js