Mozilla Central about:home search is autofocused

[sarracini]

Also see https://bugzilla.mozilla.org/show_bug.cgi?id=1382891
Split from #1974. When opening about:home it auto focuses to the search bar

[Mardak]

So we will be doing this to avoid impacting any existing search metrics.

[Mardak]

Looks like we can't use autofocus facebook/react#3066

So we'll want to detect visibility to focus but only the first visibility after the latest mount to avoid stealing focus. There's existing lib and components that individually check visibility, so potentially that can be shared and exported from https://github.com/mozilla/activity-stream/blob/master/system-addon/content-src/lib/detect-user-session-start.js

[Mardak]

We will be conservative and keep the existing focus-search-in-content behavior. But we will put this behind a pref so that we can experiment via Shield study during Beta 57 to keep focus in location bar.

The experiment will want to measure total search volume (from location bar, content, etc.) and probably go with the one that has most search. There may be per-region considerations to consider. Product to figure out details.

[Mardak]

I suppose we can use this pref name: browser.newtabpage.activity-stream.aboutHome.autoFocus

[rlr]

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