Bug 1694844 - In nsPrinterListCUPS::SystemDefaultPrinterName return NS_OK even without working CUPS. r=emilio

The other nsPrinterListCUPS methods already handle !InitOkay() without returning an error or rejecting
the promise.

Differential Revision: https://phabricator.services.mozilla.com/D107210

toolkit/components/printing/content/print.js

@@ -875,7 +875,7 @@ var PrintEventHandler = {
     let printers;
 
     if (Cu.isInAutomation) {
-      printers = await Promise.resolve(window._mockPrinters || []);
+      printers = window._mockPrinters || [];
     } else {
       try {
         printers = await printerList.printers;

widget/nsPrinterListCUPS.cpp

@@ -180,7 +180,7 @@ nsresult nsPrinterListCUPS::SystemDefaultPrinterName(nsAString& aName) const {
   aName.Truncate();
 
   if (!CupsShim().InitOkay()) {
-    return NS_ERROR_FAILURE;
+    return NS_OK;
   }
 
   // Passing in nullptr for the name will return the default, if any.