This does the trick: run-webkit-tests --debug --no-launch-safari --verbose --nthly=100000 svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg svg/custom/js-update-path-changes.svg
ASSERTION FAILED: extensions->genericContext<SVGPathSeg>(obj) == context (WebCore/bindings/js/JSSVGPathSegListCustom.cpp:52 void WebCore::updatePathSegContextMap(KJS::ExecState*, WebCore::SVGPathSegList*, WebCore::SVGPathSeg*))
<rdar://problem/5045719>
Thanks for the report! I investigated, and found the problem. Trying to come up with a patch soon. Niko
Created attachment 13587 [details] Initial patch
Comment on attachment 13587 [details] Initial patch r=me
Landed in r20151.