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

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

Index: chrome/browser/resources/settings/printing_page/printing_page.js
diff --git a/chrome/browser/resources/settings/printing_page/printing_page.js b/chrome/browser/resources/settings/printing_page/printing_page.js
index 9c282bf3dc03443fa8f5339764568ec6a7fc7acc..fbc14d451c03269c71c194e37c338838e7091b33 100644
--- a/chrome/browser/resources/settings/printing_page/printing_page.js
+++ b/chrome/browser/resources/settings/printing_page/printing_page.js
@@ -12,6 +12,19 @@ Polymer({
       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,