User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0 Build ID: 20180130223236 Steps to reproduce: * enable webrender * visit https://blog.cloudflare.com/writing-complex-macros-in-rust-reverse-polish-notation/ * find a code block with a vertical scroll bar. Click on it and scroll with the mouse wheel, or drag the scrollbar Actual results: When trying to scroll the block element, it doesn't scroll. The whole page scrolls instead. When dragging the scrollbar, the page jumps to the top (or other place). Expected results: It should scroll the block with a scrollbar. I haven't yet find any other website with this issue. mozregression gives this: Bug 1421380 - Enable gfx.webrender.hit-test by default. r=jrmuizel This causes some mochitests to fail. MozReview-Commit-ID: J2AjM0qKVE5

This is resolved in the latest nightly. Given that the subframe on this page is also inside a floating div, this is almost certainly the same issue as bug 1434846, which was fixed by bug 1434243.