Print Preview: Support the duplex preset in PDFs.

chrome/browser/resources/print_preview/native_layer.js

 // Copyright (c) 2012 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.
 
 cr.exportPath('print_preview');
 
 /**
  * @typedef {{selectSaveAsPdfDestination: boolean,
  *            layoutSettings.portrait: boolean,
  *            pageRange: string,
@@ skipping 687 matching lines @@
       var previewGenDoneEvent = new Event(
           NativeLayer.EventType.PREVIEW_GENERATION_DONE);
       previewGenDoneEvent.previewUid = previewUid;
       previewGenDoneEvent.previewResponseId = previewResponseId;
       this.dispatchEvent(previewGenDoneEvent);
     },
 
     /**
      * Updates print preset options from source PDF document.
      * Called from PrintPreviewUI::OnSetOptionsFromDocument().
-     * @param {{disableScaling: boolean, copies: number}} options Specifies
+     * @param {{disableScaling: boolean, copies: number,
+     *          duplex: number}} options Specifies
      *     printing options according to source document presets.
      * @private
      */
     onPrintPresetOptionsFromDocument_: function(options) {
       var printPresetOptionsEvent = new Event(
           NativeLayer.EventType.PRINT_PRESET_OPTIONS);
       printPresetOptionsEvent.optionsFromDocument = options;
       this.dispatchEvent(printPresetOptionsEvent);
     },
 
@@ skipping 312 matching lines @@
       return this.serializedAppStateStr_;
     }
   };
 
   // Export
   return {
     NativeInitialSettings: NativeInitialSettings,
     NativeLayer: NativeLayer
   };
 });