One other possible-shot-in-the-dark: the blank area might be about the size that devtools would be if I had devtools open (though I don't have devtools open). If I do open devtools, then of course the bug goes away (but I did notice that devtools nicely filled the blank area).
Bug 1752942 Comment 1 Edit History
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One other possible-shot-in-the-dark: the blank area might be about the size that devtools would be if I had devtools open (though I don't have devtools open). If I do open devtools, then of course the bug goes away (but I did notice that devtools nicely filled the blank area, which might be a clue or might not be).