It ends up being like microsoft’s embrace and extend, but (so far) without the extinguish. Or, put another way, a sufficiently large PUBLIC corp cannot “do no evil”.

Although, to look from the other direction, if it’s completely open and Chrome doesn’t have special undocumented hooks into it – there’s no reason the ohter browsers can’t just join in if Dart turns out to rock more than JS. Sometimes you have to just break clean – you can’t improve what’s already there.