It is possible that the patch in 192828 fixes this. My laptop overheats whenever I try to build webkit, so I haven't been able to test with the patch yet, although I can confirm that epiphany 3.31.3 is affected. I also got my friend to test STP and release safari on his mac, and they seem to hang too. The crashing page is <https://cras.sh>.
The test site no longer appears to be present.