Re: Brittle software?
It is absolutely clear Google did this specifically to break the hardware acceleration on other browsers - probably more targeted at mobile than desktop since that's where power usage matters more. Chrome could skip this particular empty div tag since it "knows" what it is for. If other browsers ignored it on this site, Google could make it do something (after addressing this in a Chrome update) and then those browsers are "broken" on Youtube.
Google is 100% in the wrong here, and have been caught with their pants down. Sad to see people defending such evil and anti-competitive behavior. The FTC should look into forcing them to spin off Chrome, a company that controls so many important web destinations has no business being involved on the browser side as well. This episode clearly demonstrates why.