Spinoff from bug 1406008 comment 9, it looks like there are still conditions where we try to delete invalid animations. Jan Andre Ikenmeyer [:darkspirit] from bug 1406008 comment 9: > I ran a clone of my main profile in Linux x64 debug and activated highlight > painted areas: I activated and deactivated autoscoll to be able to scroll > down on https://www.golem.de. After switching to another tab, switching back > and scrolling down 1/3 of the page, scrolling stopped (against my will) and > I got this in my terminal while all text on the lower half of the page had a > red background: > > [GPU 15174, Compositor] ###!!! ASSERTION: Tried to delete invalid animation: 'Error', file /builds/worker/workspace/build/src/gfx/layers/wr/WebRenderBridgeParent.cpp, line 420 > Besides this I didn't get any message that could explain to me why scrolling > by mousewheel didn't work after switching to this tab. Note that Jan's default profile uses a light or dark theme, as opposed to the default. That might be important. This is not really user-visible in release builds so low priority, but the root cause might manifest in other ways that *are* user-visible.

Oh I meant two middle clicks to activate/deactivate autoscroll for being able to scroll (bug 1406008). And of course I did this after switching tabs, but before I scrolled down.

And I'm using the dark theme.