Aha, it's `-webkit-fill-available` -- this works properly if I have that pref toggled to `true`. (And
Bug 1954955 Comment 3 Edit History
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Aha, it's `-webkit-fill-available` -- this works properly if I have that pref toggled to `true`. (And it's specifically a rule for `html, body { height: -webkit-fill-available}` that matters here -- that needs to be set and honored before you click the downarrow button, presumably because the site does some geometry measurement and ends up broken or working depending on the height that it measures.)