[Bug] Floorp only the first window can properly use scripts

[black-ish]

I had been meaning to implement proper mouse gestures and noticed that they work fine in the first(main) window but not in the second or third and so on window.

I don't know how to debug that as I don't understand enough of it.

Steps to reproduce:

• Download & install Floorp
• Start Floorp to create a profile
• Install userChromeJS
• Install mousegestures from here
• Use "Clear startup cache…" in about:support
• Open a second window with Ctrl+N for example
• Try to use gesture in second window

Things like TabMixPlus seem to work properly it seems.
But anything else only works in the first window but not any other.