Emitted after an extension is loaded. This occurs whenever an extension is added to the "enabled" set of extensions. This includes:* Extensions being loaded from Extensions.loadExtension.* Extensions being reloaded: * from a crash. * if the extension requested it (chrome.runtime.reload()).

Emitted after an extension is loaded and all necessary browser state is initialized to support the start of the extension's background page.

Emitted after an extension is unloaded. This occurs when Session.removeExtension is called.