Bug 1660589 - Localize paper names only on macOS and not Linux r=jwatt

Paper names should be localized on macOS, but on linux we want to use
the PWG standardized media name.

Differential Revision: https://phabricator.services.mozilla.com/D87936

widget/nsPrinterCUPS.cpp

@@ -94,10 +94,15 @@ void nsPrinterCUPS::GetPrinterName(nsAString& aName) const {
 
 const char* nsPrinterCUPS::LocalizeMediaName(http_t& aConnection,
                                              cups_size_t& aMedia) const {
+// We want to localize the name on macOS, but not on Linux.
+#ifdef XP_MACOSX
   // The returned string is owned by mPrinterInfo.
   // https://www.cups.org/doc/cupspm.html#cupsLocalizeDestMedia
   return mShim.cupsLocalizeDestMedia(&aConnection, mPrinter, mPrinterInfo,
                                      CUPS_MEDIA_FLAGS_DEFAULT, &aMedia);
+#else
+  return nullptr;
+#endif
 }
 
 bool nsPrinterCUPS::SupportsDuplex() const {

widget/nsPrinterCUPS.h

@@ -43,6 +43,7 @@ class nsPrinterCUPS final : public nsPrinterBase {
 
   /**
    * Retrieves the localized name for a given media (paper).
+   * Returns nullptr if the name cannot be localized.
    */
   const char* LocalizeMediaName(http_t& aConnection, cups_size_t& aMedia) const;