Don't switch to CF's active document for frames or iframes....

chrome_frame/test/data/chrome_frame_tester_helpers.js

 //
 // This script provides some mechanics for testing ChromeFrame
 //
 function onSuccess(name, id) {
   onFinished(name, id, "OK");
 }
 
 function onFailure(name, id, status) {
   onFinished(name, id, status);
 }
 
 function getXHRObject(){
   var XMLHTTP_PROGIDS = ['Msxml2.XMLHTTP', 'Microsoft.XMLHTTP',
                          'Msxml2.XMLHTTP.4.0'];
   var http = null;
   try {
     http = new XMLHttpRequest();
   } catch(e) {
   }
-  
+
   if (http)
     return http;
-  
+
   for (var i = 0; i < 3; ++i) {
     var progid = XMLHTTP_PROGIDS[i];
     try {
       http = new ActiveXObject(progid);
     } catch(e) {
   }
 
   if (http)
     break;
   }
@@ skipping 99 matching lines @@
 
   return false;
 }
 
 function reloadUsingCFProtocol() {
   var redirect_location = "cf:";
   redirect_location += window.location;
   window.location = redirect_location;
 }
 
+function isRunningInChrome() {
+  var is_chrome = /chrome/.test(navigator.userAgent.toLowerCase());
+  return is_chrome;
+}
+
 function TestIfRunningInChrome() {
-  var is_chrome = /chrome/.test(navigator.userAgent.toLowerCase());
-  if (!is_chrome) {
+  var is_chrome = isRunningInChrome();
+  if (!isRunningInChrome()) {
     onFailure("ChromeFrameWindowOpen", "Window Open failed :-(",
-                "User agent = " + navigator.userAgent.toLowerCase());
+              "User agent = " + navigator.userAgent.toLowerCase());
   }
   return is_chrome;
 }