Maybe I'm misunderstanding something here.

This reads like Google is now attempting to dictate the direction Javascript goes in, by implementing proposals before they've become standards, and shipping them in their browser. Given the dominance of the browser engine, it effectively sets the direction of the language, particularly if people start to use it (which they will).

This is feeling like IE6 all over again. We're getting non-standard implementations of standards, that will further encourage websites to be "Chrome only".