This avoids a lot of mismatches between nsAString and char16_t*, thus removing
many getter_Copies() and ToNewUnicode() and get() calls, and generally making
things simpler.
Note: the patch removes GetDefaultPrinterNameFromGlobalPrinters() by simply
inlining it at its two callsites, which is easy with the changed types.
nsXPIDLStrings are marked as VOIDED upon initialization. Most of these local
nsXPIDLString variables are immediately set via getter_Copies(), which will
either assign a string value (using Adopt()) or do SetIsVoid(). These can be
trivially converted to nsString, which will get the same treatment.
The patch suitably converts the remaining nsXPIDLString local variable as well.
GTK versions prior to 2.24 incorrectly advertise themselves as able to print PDFs,
even when they can't. We were wholesale setting the output format to PostScript for
these older GTK versions, without giving the user the opportunity to override
it. We now lazily determine whether or not the output should be in PostScript,
which should give the user the opportunity to override.
In the multi-process case, we might need to query the system (and maybe the
network) for a printer with a name matching the one we're looking for. In
order to not spin an event loop at dangerous times (since searching for printers
is either asynchronous, or requires an event loop), we defer searching for
the printer until we've already finished reflowing and rendering the document
to be printed.
