r84147, 2001 leaks
r84152, 6343 leaks
Check out the "view leaks" URLs on those build pages to see the leaks.
Most/all of the leaks seem to be beneath the Document constructor.
Seem like SVG documents are leaking:
2968 WebCore::XMLDocumentParser::append(WebCore::SegmentedString const&)
340 WebCore::SVGDocument::create(WebCore::Frame*, WebCore::KURL const&
This is very likely https://bugs.webkit.org/show_bug.cgi?id=59072.
We are leaking piles of SVG documents. 84151 is likely a red herring, it just made the leaks visible to the leaks checker (probably by removing a document back reference).
This seems not to be happening anymore.