12b36d5d_ebug_Preferences___FirebugWiki__Option
[Description] Specifies whether browser and extensions internal source files shall be shown inside the Script Panel. Note that Firebug will still not activate for chrome URLs unless you also set filterSystemURLs to false. [Valid Values] true, false [Default] false [UI Equivalents] Script Panel Options Mini Menu->Show chrome sources [Option] 
service.showAllSourceFiles
Firebug Preferences - FirebugWiki