Add DPI option selection to Print Preview.

chrome/browser/resources/print_preview/data/app_state.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.define('print_preview', function() {
   'use strict';
 
   /**
    * Object used to get and persist the print preview application state.
    * @constructor
@@ skipping 22 matching lines @@
    * @enum {string}
    */
   AppState.Field = {
     VERSION: 'version',
     SELECTED_DESTINATION_ID: 'selectedDestinationId',
     SELECTED_DESTINATION_ACCOUNT: 'selectedDestinationAccount',
     SELECTED_DESTINATION_ORIGIN: 'selectedDestinationOrigin',
     SELECTED_DESTINATION_CAPABILITIES: 'selectedDestinationCapabilities',
     SELECTED_DESTINATION_NAME: 'selectedDestinationName',
     IS_GCP_PROMO_DISMISSED: 'isGcpPromoDismissed',
+    DPI: 'dpi',
     MEDIA_SIZE: 'mediaSize',
     MARGINS_TYPE: 'marginsType',
     CUSTOM_MARGINS: 'customMargins',
     IS_COLOR_ENABLED: 'isColorEnabled',
     IS_DUPLEX_ENABLED: 'isDuplexEnabled',
     IS_HEADER_FOOTER_ENABLED: 'isHeaderFooterEnabled',
     IS_LANDSCAPE_ENABLED: 'isLandscapeEnabled',
     IS_COLLATE_ENABLED: 'isCollateEnabled',
     IS_CSS_BACKGROUND_ENABLED: 'isCssBackgroundEnabled',
     VENDOR_OPTIONS: 'vendorOptions'
@@ skipping 161 matching lines @@
     persist_: function() {
       chrome.send(AppState.NATIVE_FUNCTION_NAME_,
                   [JSON.stringify(this.state_)]);
     }
   };
 
   return {
     AppState: AppState
   };
 });