[CUPS] Put the CUPS settings UI behind a command line flag --enable-native-cups.

chrome/browser/resources/settings/printing_page/printing_page.js

 // Copyright 2016 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.
 
 Polymer({
   is: 'settings-printing-page',
 
   properties: {
     /** Preferences state. */
     prefs: {
       type: Object,
       notify: true,
     },
 
+<if expr="chromeos">
+    /**
+     * Whether to show CUPS printers settings.
+     * @private {boolean}
+     */
+    showCupsPrintingFeatures_: {
+      type: Boolean,
+      value: function() {
+        return loadTimeData.getBoolean('showCupsPrintingFeatures');
+      },
+    },
+</if>
+
     /** @type {!Array<!CupsPrinterInfo>} */
     cupsPrinters: {
       type: Array,
       notify: true,
     },
 
     searchTerm: {
       type: String,
     },
   },
@@ skipping 13 matching lines @@
     settings.navigateTo(settings.Route.CUPS_PRINTER_DETAIL);
     this.$.arraySelector.select(event.detail);
   },
 </if>
 
   /** @private */
   onTapCloudPrinters_: function() {
     settings.navigateTo(settings.Route.CLOUD_PRINTERS);
   },
 });