While making PR for Ripple team (https://issues.apache.org/jira/browse/RIPPLE-26), a really elegant way of accessing child window/frame was found.
Now we use global variable 'bsPopup' for accesing BrowserSim, which is not really neat solution:

• Implementation is tightly coupled with BrowserSim;
• Problems with merging original ripple source code;
• Have no possibility of patch sending to the ripple team;

There is a need in replacement all global bsPopup usage to:

  var emulatorBridge = ripple('emulatorBridge');
   .
   .
   .
   emulatorBridge.window();