I could see plausibly assigning blame any combination of the browser (a beta version at that), the OS, or video drivers, but instead you're seriously going to blame a web page for locking up your machine? Is that really how low we want to set that bar?
i'm running 55.0b13 (64-bit) firefox on windows 10 and clicking on that demo froze the browser, froze my box - hard reboot.
whatever you're doing some of it's wrong. bad wrong.