As mentioned in http://developers.google.com/chart/interactive/docs/basic_load_libs#update-library-loader-code , it is advised to upgrade from old jsapi to new gstatic...loader.js for google charts.
Problem: Currently I'm having callback that is executed after loading of the js file completed: http://www.google.com/jsapi?callback=oldCallback
But with the new library, this callback is never executed:
http://www.gstatic.com/charts/loader.js?callback=newCallback
Why?
Example: https://jsfiddle.net/rLo9vdqm/1/