Bug 1329216 - Move default printer name querying. r=bobowen

dom/base/nsGlobalWindow.cpp

@@ -7776,7 +7776,19 @@ nsGlobalWindow::PrintOuter(ErrorResult& aError)
 
         nsXPIDLString printerName;
         printSettings->GetPrinterName(getter_Copies(printerName));
-        if (printerName.IsEmpty()) {
+
+        bool shouldGetDefaultPrinterName = printerName.IsEmpty();
+#ifdef MOZ_X11
+        // In Linux, GTK backend does not support per printer settings.
+        // Calling GetDefaultPrinterName causes a sandbox violation (see Bug 1329216).
+        // The printer name is not needed anywhere else on Linux before it gets to the parent.
+        // In the parent, we will then query the default printer name if no name is set.
+        // Unless we are in the parent, we will skip this part.
+        if (!XRE_IsParentProcess()) {
+          shouldGetDefaultPrinterName = false;
+        }
+#endif
+        if (shouldGetDefaultPrinterName) {
           printSettingsService->GetDefaultPrinterName(getter_Copies(printerName));
           printSettings->SetPrinterName(printerName);
         }

layout/printing/nsPrintEngine.cpp

@@ -980,6 +980,13 @@ nsPrintEngine::CheckForPrinters(nsIPrintSettings* aPrintSettings)
   // Mac doesn't support retrieving a printer list.
   return NS_OK;
 #else
+#if defined(MOZ_X11)
+  // On Linux, default printer name should be requested on the parent side.
+  // Unless we are in the parent, we ignore this function
+  if (!XRE_IsParentProcess()) {
+    return NS_OK;
+  }
+#endif
   NS_ENSURE_ARG_POINTER(aPrintSettings);
 
   // See if aPrintSettings already has a printer

toolkit/components/printingui/ipc/PrintingParent.cpp

@@ -129,14 +129,24 @@ PrintingParent::ShowPrintDialog(PBrowserParent* aParent,
   rv = settings->SetPrintSilent(printSilently);
   NS_ENSURE_SUCCESS(rv, rv);
 
+  nsXPIDLString printerName;
+  settings->GetPrinterName(getter_Copies(printerName));
+#ifdef MOZ_X11
+  // Requesting the default printer name on Linux has been removed in the child,
+  // because it was causing a sandbox violation (see Bug 1329216).
+  // If no printer name is set at this point, use the print settings service
+  // to get the default printer name.
+  if (printerName.IsEmpty()) {
+    mPrintSettingsSvc->GetDefaultPrinterName(getter_Copies(printerName));
+    settings->SetPrinterName(printerName);
+  }
+  mPrintSettingsSvc->InitPrintSettingsFromPrinter(printerName, settings);
+#endif
+
   // If this is for print preview or we are printing silently then we just need
   // to initialize the print settings with anything specific from the printer.
   if (isPrintPreview || printSilently ||
       Preferences::GetBool("print.always_print_silent", printSilently)) {
-    nsXPIDLString printerName;
-    rv = settings->GetPrinterName(getter_Copies(printerName));
-    NS_ENSURE_SUCCESS(rv, rv);
-
     settings->SetIsInitializedFromPrinter(false);
     mPrintSettingsSvc->InitPrintSettingsFromPrinter(printerName, settings);
   } else {