How to get the URL of the frame in chrome browser
Solution 1:
Right-clicking on the frame should show you the option "View frame source". By clicking on it, it will open the source code in a new tab. Its URL is on the address bar. Just have to ignore to remove the "view-source:" prefix, though.
Solution 2:
Try using "Inspect Element" over desired frame. You will see original frameset HTML code and selected page code nested.