MD Settings: Add "Show Google Now cards in the launcher" row in Search section.

chrome/test/data/webui/settings/search_page_test.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('settings_search_page', function() {
   function generateSearchEngineInfo() {
     var searchEngines0 = settings_search.createSampleSearchEngine(
         true, false, false);
     searchEngines0.default = true;
     var searchEngines1 = settings_search.createSampleSearchEngine(
@@ skipping 130 matching lines @@
           assertTrue(!!checkbox);
           assertFalse(checkbox.disabled);
           assertFalse(checkbox.checked);
           MockInteractions.tap(checkbox.$.checkbox);
           Polymer.dom.flush();
           return browserProxy.whenCalled('setHotwordSearchEnabled');
         }).then(function() {
           assertTrue(browserProxy.hotwordSearchEnabled);
         });
       });
+
+      test('UpdateGoogleNowOnPrefChange', function() {
+        return browserProxy.whenCalled('getGoogleNowAvailability').then(
+            function() {
+          Polymer.dom.flush();
+          assertTrue(page.googleNowAvailable_);
+
+          var checkbox = page.$$('#googleNowEnable');
+          assertTrue(!!checkbox);
+          assertFalse(checkbox.disabled);
+          assertFalse(checkbox.checked);
+
+          page.prefs = {
+            google_now_launcher: {
+              enabled: {
+                type: chrome.settingsPrivate.PrefType.BOOLEAN,
+                value: true,
+              }
+            }
+          };
+          Polymer.dom.flush();
+          assertFalse(checkbox.disabled);
+          assertTrue(checkbox.checked);
+        });
+      });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });