Configure CKEditor plugin
You can define (extra) config options in a CKEditor profile. Go to example.com/admin/config/content/ckeditor then select the editor profile(s) in which you have enabled autosave and go to the "Advanced Options".

In the "Custom JavaScript configuration" field you can override config options like 

config.autosave_saveDetectionSelectors = "a[href^='javascript:__doPostBack'][id*='Save'],a[id*='Cancel']";
config.autosave_delay = 5;


No need to alter any of the javascript files.