cros: Use runtime stylus detection for ash palette.

chrome/test/data/webui/settings/device_page_tests.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.
 
 cr.define('device_page_tests', function() {
   /** @enum {string} */
   var TestNames = {
     DevicePage: 'device page',
     Display: 'display',
     Keyboard: 'keyboard',
@@ skipping 11 matching lines @@
   }
 
   TestDevicePageBrowserProxy.prototype = {
     /** override */
     initializePointers: function() {
       // Enable mouse and touchpad.
       cr.webUIListenerCallback('has-mouse-changed', true);
       cr.webUIListenerCallback('has-touchpad-changed', true);
     },
 
+    /** override */
+    initializeStylus: function() {
+      // Enable stylus.
+      cr.webUIListenerCallback('has-stylus-changed', true);
+    },
+
     /** @override */
     handleLinkEvent: function(e) {
       settings.DevicePageBrowserProxyImpl.prototype.handleLinkEvent.call(
           this, e);
       // Prevent opening the link, which can block the test.
       e.preventDefault();
     },
 
     /** override */
     initializeKeyboard: function() {},
@@ skipping 656 matching lines @@
               settings.DevicePageBrowserProxyImpl.getInstance().powerSourceId_);
         });
       });
     });
   });
 
   return {
     TestNames: TestNames
   };
 });