What exactly are you trying to do? Tying app behavior to a channel is an anti-pattern, as the channels are constantly evolving. If you are interested in restricting functionality to a specific new feature, then use minimum_chrome_version in your manifest, or if you don't want to restrict availability of your product during the (generally) brief window between dev and stable, simply parse navigator.userAgent (or navigator.appVersion, as you say) for the Chrome version, then switch your app's behavior based on whether you're before or at the version you need for the functionality in question.
Again, don't require a specific channel. It frustrates users and is a maintenance headache for you.