Fixed with https://github.com/wikimedia/WhoWroteThat/pull/145

Should we merge this with: P10183

TIL: You can't merge pastes with tasks. But I made a nice comment on the paste: https://phabricator.wikimedia.org/P10183#59317

For each of the five supported wikis, loaded a random article both with the Welcome Tour popup and without it.

Each time, checked that there were no errors in the console, that WWT could be launched and highlighting and revision popups appeared.

Repeated this on Firefox 68 and Chromium 73.

Repeated this both as an anonymous user and as my own user (who has a few gadgets enabled, like Twinkle, in case this makes a difference).

Version: commit a4b165b9260f15e96313a1596064275a918c9dff (latest as of now) which I built myself.

@ifried I am moving this into Product Sign-Off, but it has yet to be released to the Chrome Store or Firefox Addons.

Both browser stores have now been updated with 0.14.0.