Embrace, Extend, Exsanguinate.

There were warnings years ago when Google first shipped Chrome that this is the script they were following. By promoting the idea that they were "open source" they could grab the good will of people, and then, over time, slowly lock up what had previously been open.

Like was warned years ago, now that they have such market dominance, they can dictate web standards without having to go through the W3C or consulting pretty much anyone else for that matter. With their dominance in the browser market, they can essentially "break" tons of websites for other browsers, limiting the ability of other browsers to say "no, we don't want WEI." It will be a case of "okay, but if you don't implement it, get ready to never be able to view YouTube or use Gmail ever again in a browser that doesn't support WEI." Because at that point, they will be forcing WEI through every Google service, essentially forcing other browsers to adopt it or be unable to use Google.