detecting Android WebView from Javascript/HTML

I'm working on a web application which will normally be accessed from the Android browser, but I need it to display alternate content if it is loaded in a WebView from an Android app. I've been looking for any telltale differences in the UA string or the DOM, but I haven't been able to find any. (Note: I do not cont开发者_如何学运维rol the third-party Android apps, so I cannot make changes to their code.) Are there any ways to detect the WebView from Javascript?