Closetab cesar

Started off doing a text search. The best I can do for search was the expression 'close tab'. I got many .properties files, and I don't know what they are for.

Got here which brought me to a function with this signature :

openLinksInTabs: function PC_openLinksInTabs()

This is not quite what I'm looking for, I think this link is to open all the links in a folder.
I did some more searching and found how firefox closes a tab/browser in javascript here with this signature :

function BrowserCloseTabOrWindow()

Which has #ifdefs. But it was what I was looking for. Trying to look for what defines this; instead I found a function that calls it here I think that's the end of the line. I haven't brushed up on my javascript, but nothing defines the function removeCurrentTab(). All further searches was fruitless