On ToT, Chrome will block if initial URL is extension, showing 
 
 <factory_test_extension_id> is blocked
 Requests to the server have been blocked by an extension
 Try disabling your extensions.
 ERR_BLOCKED_BY_CLIENT
   [Reload]

If we set init page to http://localhost:4012 then it would work, but due to  http://crbug.com/627372 , we won't be able to get focus in the first created window.

If we use Chrome remote debugging protocol (chrome_openurl in factory bin) then the window will have focus properly.