sanitization for video-swap-new-ublock-origin.js & vaft-ublock-origin.js

[ryanbr]

Wanting to merge the uBO scripts into Brave. brave/adblock-resources#160

Some sanitization issues on the script, is something can be addressed upstream? Or safe to ignore?

[pixeltris]

It doesn't look like anything too crazy to me. If you want to fix them up PRs are welcome but I'm unlikely to do that myself.

FYI I don't know how Brave's script injection works but there's some issue with the scripts randomly not getting injected with userResourcesLocation. Might be worth looking at #200