Chrome's behavior here on images 2 and 3 (with unspecified height and `max-width:max-content`) seems to be to use `max-width: stretch` essentially, aka `max-width: -webkit-fill-available`. (Similar to `max-width:100%`, but calibrated to fill the available space even if there's a thick border on the image and max-width is being applied to the content-box size.)
Bug 1929151 Comment 2 Edit History
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Chrome's behavior here (for the img elements that we don't render -- the ones with auto `height` and with `max-width:max-content`) seems to be to use `max-width: stretch` essentially, aka `max-width: -webkit-fill-available`. (Similar to `max-width:100%`, but calibrated to fill the available space even if there's a thick border on the image and max-width is being applied to the content-box size.)