According to Google Developers, the UA string looks like this:
Mozilla/5.0 (iPhone; U; CPU iPhone OS 5_1_1 like Mac OS X; en) AppleWebKit/534.46.0 (KHTML, like Gecko) CriOS/19.0.1084.60 Mobile/9B206 Safari/7534.48.3
Where it differs from iOS Safari in that it says CriOS instead of Version. So this:
if(navigator.userAgent.match('CriOS'))
Should do it.