Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product. (More info)
Created attachment 635587[details][diff][review]
not entirely sure what the convention is, but it seems like this code is relying on neg32() setting condition codes, so I say let's go with it.