This free tool logs when an extension is installed, uninstalled, upgraded, disabled or enabled. It keeps track of all your old extensions, as well as current and past states of the extensions still installed. You can view a table with extension name, state (enabled, disabled, uninstalled), type, or id, and keep track of each chrome update. You can also view a table of all the installed extensions. 

The EL (Extension Log) tool has an event table that contains the logs of events that occurred with each extension. This table has one field per extension and contains the id, status, name, message, start time and end time of each event. If an event occurred, EL displays the message in the application and logs the event. 

You can also export the whole log history, and save extension packages in its original format or as a zip file. You can import extensions and chrome version history from a backup. Import of events is still in beta. EL allows you to save extension packages in its original format or as a zip file. You can import options, and chrome version history from a backup.