As I look into making our use counter reporting work with Fission in bug 1656114, I noticed that layout/reftests/svg/as-image/img-blobURI-2.html tests that an SVG image can itself have an <image> with a blob: URL that is also an SVG image. The way we propagate image document use counters (in VectorImage::OnSVGDocumentLoaded -> ... -> nsImageLoadingContent::Notify -> VectorImage::PropagateUseCounters) misses propagating any use counters reported by the blob: URL document, since we end up dispatching the SVG load event of the outer SVG image before the blob: URL document.

This is an existing issue which I don't plan to fix as part of bug 1656114.

Assuming tagging this with wr-82 was a mistake? Nothing webrender specific about this that I can tell.