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 377447[details][diff][review]
We can assert while scrolling if the reflow was interrupted, because ComputeRepaintRegionForCopy builds a display list but doesn't disable usedX asserts. Patch attached.