toolkit/components/startup/public/nsIAppStartup.idlScriptable
This lets you get information about the times at which key application startup events occurred.
1.0
66
Introduced
Gecko 2.0
Inherits from: nsISupports Last changed in Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1)

In Gecko 4.0 this Interface was merged into the nsIAppStartup interface.