Blinking frames on first loop in Firefox

[Zulko]

When displaying a GIX on Firefox, the first loop is blinky (typically, frame / black screen / new frame / black screen / etc.), as every frame from a GIF or video source appears with a lag. This is due to a known SVG rendering issue (see this discussion), and I never found a workaround. A radical solution could be to switch from SVG-based rendering to Canvas rendering.