PrintPreview: Added a helper function to get print job settings from dictionary.

printing/printing_context_mac.mm

Index: printing/printing_context_mac.mm
diff --git a/printing/printing_context_mac.mm b/printing/printing_context_mac.mm
index cf6ea9f9498ed8fe18d04a2fe565fd0d8824037b..9357e77c99e437bc1c741c23d513764e8c60e49d 100644
--- a/printing/printing_context_mac.mm
+++ b/printing/printing_context_mac.mm
@@ -11,7 +11,6 @@
 #include "base/mac/scoped_cftyperef.h"
 #include "base/sys_string_conversions.h"
 #include "base/values.h"
-#include "printing/print_job_constants.h"
 #include "printing/print_settings_initializer_mac.h"
 
 namespace printing {
@@ -93,14 +92,12 @@ PrintingContext::Result PrintingContextMac::UpdatePrintSettings(
   print_info_.reset([[NSPrintInfo sharedPrintInfo] copy]);
 
   bool landscape;
-  if (!job_settings.GetBoolean(kSettingLandscape, &landscape))
-    return OnError();
-  settings_.SetOrientation(landscape);
-
   std::string printer_name;
-  if (!job_settings.GetString(kSettingPrinterName, &printer_name))
+  if (!GetSettingsFromDict(job_settings, &landscape, &printer_name))
     return OnError();
 
+  settings_.SetOrientation(landscape);
+
   if (!SetPrinter(printer_name))
     return OnError();