https://hg.mozilla.org/mozilla-central/annotate/tip/browser/base/content/browser.xul#l225 There are two options here. We can re-implement this as HTML inside urlbarView-body-inner, or we can just copy the XUL implementation as a sibling to urlbarView-body-outer.

Can we take the HTML option here? We need to assume that the whole bar needs to be flexible and possible to easily create experiments for. This may include the one-off search options and their design or their visibility entirely. Thus, if possible, there'd be some kind of template - configurable so that future experiment addons can swap it out with something else - that'd define the structure here. Extensibility is a primary objective for the view parts.

This is just about the search suggestions notification, the one-off buttons are bug 1491248. HTML is probably what we'll want eventually, although with bug 1033225 and XUL widgets being ported to Custom Elements, the differences will become minor. Anyway, even assuming we'll eventually want HTML, copying and pasting the XUL structure might juts be trivial enough to be a reasonable shortcut for the first milestone where our focus is parity with the old implementation.

Currently on the first 4 focuses of the urlbar we show a search suggestions hint inside the urlbar panel, with a button that opens search preferences allowing the user to disable suggestions. This was both for privacy (allow to disable before first use) and discoverability of the feature. If we want to continue using this approach to notify, we must port it. Anyway we must do something about it. I'm ni? Verdi to evaluate the current approach and see if we should keep it as-is or change to a different kind of notification.