lefteris what is the purpose of this file?
As I mentioned on this posting
the index.html file is Google Maps page. It will open google maps at the location that user clicked on the ESRI map. For this page to be functional, it will need the Google API key. On this page you will be presented the option to view Streetview or GE.
the ndex page is called on line #42 of the widget.js of the https://community.esri.com/docs/DOC-13056-googletoolszip