Comment 127 for bug 10910

Comment on attachment 500694
don't use PS prefs in gtk

However, the way that this patch avoids the arbitrary default adds to the
existing confusion. It works because the pref lookup no longer matches the
pref setting. It would be better to remove the pref and the lookup code.
http://hg.mozilla.org/mozilla-central/annotate/a66254dfa588/modules/libpref/src/init/all.js#l3065

One of the (many) strange things about the print setup code, is that the list
of (basic standard) paper sizes is only added to
print.tmp.printerfeatures.paper.* if a paper_size pref is found, and that will
rarely be anything but "print.postscript.paper_size".
http://hg.mozilla.org/mozilla-central/annotate/7a3469118cf3/widget/src/gtk2/nsDeviceContextSpecG.cpp#l898
(The initial implementation was added in bug 132563.)

print.tmp.printerfeatures.paper.* is only used from
toolkit/components/printing/content/printjoboptions.js, as a set of available
paper sizes. AFAICS however, that is only used if
nsPrintingPromptService::ShowPrintDialog cannot find nsIPrintDialogService.
Now that the GTK port provides a nsIPrintDialogService, there is no need to
set up print.tmp.printerfeatures.paper.*

So it safe to remove the whole paper_size block
http://hg.mozilla.org/mozilla-central/annotate/7a3469118cf3/widget/src/gtk2/nsDeviceContextSpecG.cpp#l883