When landing bug 974745 we introduced inline event handlers to newTab.xul, which we really shouldn't use anymore because they're bad style. Please always use .addEventListener() etc. for event handling.

I don't follow. By inline event handlers you mean addEventListener(event, event => {}); instead of addEventListener(event, this); ... handleEvent: function (event) {}? Why is that bad style? Re: always using .addEventListener() for event handling, what other than addEventListener do you use to handle events?

No, I was talking about onclick="foo.bar()" or onsubmit="foo.baz()". Inline like in "inline styles", not sure if that's the correct term.

Gotcha, thanks.

https://hg.mozilla.org/integration/fx-team/rev/040440348215 qa- for already covered by automated tests