Google/Chrome also works hard to support "what's already out there", which is what you mention, but what we're discussing now is building on your supposedly-open-but-really-proprietary platform _against_ other players, whether that's policy or coincidental with constraints.

Microsoft spent effort making sure Windows itself WON'T run on DR DOS before that. They constantly ignored web standards after they won the browser wars (conveniently working well with Microsoft tools that produced non-standard markup, though) ... up until the moment they lost them again, at which point they started to pay attention to standards again.

With their last few releases, Google seems to be adopting this Microsoft style of evil. Some people defend that, and some don't.