Add an API for hosted apps to check their install and running states.

chrome/test/data/extensions/get_app_details_for_frame.html

 <script>
 function testUnsuccessfulAccess() {
   try {
     chrome.app.getDetailsForFrame(frames[0]);
   } catch (e) {
     if (e.indexOf("Access denied") == 0)
       return true;
     else
       throw e;
   }
   return false;
 }
 
 function getFrameURL(host) {
   var result = "http://" + host;
   if (location.port) {
     result += ":";
     result += location.port;
   }
   result += location.pathname;
   return result;
 }
 
-var iframe = document.createElement("iframe");
-iframe.src = getFrameURL("app.com");
-document.documentElement.appendChild(iframe);
+function newFrame(host) {
+  if (frames.length > 0)
+    document.documentElement.removeChild(document.querySelector('iframe'));
+  var iframe = document.createElement("iframe");
+  iframe.src = getFrameURL(host);
+  document.documentElement.appendChild(iframe);
+}
+
+newFrame('app.com');
+
 </script>