It runs in the parent process (which maybe means it doesn't have apz) and suffers from long display list build times because it has large blocks of text. It also seems to have a blob image issue (perhaps because of borders)
Bug 1635633 Comment 14 Edit History
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about:support runs in the parent process (which maybe means it doesn't have apz) and suffers from long display list build times because it has large blocks of text. It also seems to have a blob image issue (perhaps because of borders)