Golly gee, web development sure seems to be getting complicated. Do you think there will ever be tools that can test web pages against a diversity of browsers in order to catch this sort of problem before it hits production?
Maybe an Apple intern could sit in front of a computer that runs ImageMagick's compare utility. However, it stands to reason that Apple would be left with a choice between hiring two interns and not having an intern write their production code. Or maybe Apple could have the intern work on automating a visual testing process so that builds break when they break other browsers.
But I never said anything about "automating" since even manual testing would be a QA improvement.