PrintPreview: Added code to identify the printer default duplex value.

printing/printing_context_mac.mm

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "printing/printing_context_mac.h"
 
 #import <ApplicationServices/ApplicationServices.h>
 #import <AppKit/AppKit.h>
 
 #include "base/logging.h"
@@ skipping 218 matching lines @@
 
 bool PrintingContextMac::SetDuplexModeInPrintSettings(DuplexMode mode) {
   PMDuplexMode duplexSetting;
   switch (mode) {
     case LONG_EDGE:
       duplexSetting = kPMDuplexNoTumble;
       break;
     case SHORT_EDGE:
       duplexSetting = kPMDuplexTumble;
       break;
-    default:
+    case SIMPLEX:
       duplexSetting = kPMDuplexNone;
       break;
+    default:  // UNKNOWN_DUPLEX_MODE
+      return true;
   }
 
   PMPrintSettings pmPrintSettings =
       static_cast<PMPrintSettings>([print_info_.get() PMPrintSettings]);
   return PMSetDuplex(pmPrintSettings, duplexSetting) == noErr;
 }
 
 bool PrintingContextMac::SetOutputColor(int color_mode) {
   PMPrintSettings pmPrintSettings =
       static_cast<PMPrintSettings>([print_info_.get() PMPrintSettings]);
@@ skipping 123 matching lines @@
 void PrintingContextMac::ReleaseContext() {
   print_info_.reset();
   context_ = NULL;
 }
 
 gfx::NativeDrawingContext PrintingContextMac::context() const {
   return context_;
 }
 
 }  // namespace printing