MD Settings: Show "Set date and time" button when relevant

chrome/test/data/webui/settings/date_time_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.
 
 (function() {
   function getFakePrefs() {
     return {
       cros: {
         system: {
           timezone: {
@@ skipping 217 matching lines @@
         cr.webUIListenerCallback('time-zone-auto-detect-policy', false);
         verifyAutoDetectSetting(true);
         verifyPolicy(false);
 
         // User can disable auto-detect.
         MockInteractions.tap(dateTime.$.timeZoneAutoDetectCheckbox);
         verifyAutoDetectSetting(false);
         done();
       });
     });
+
+    test('set date and time button', function() {
+      dateTime = initializeDateTime(getFakePrefs(), false);
+
+      var showSetDateTimeUICalled = false;
+      registerMessageCallback('showSetDateTimeUI', null, function() {
+        assertFalse(showSetDateTimeUICalled);
+        showSetDateTimeUICalled = true;
+      });
+
+      var setDateTimeButton = dateTime.$.setDateTime;
+      assertEquals(0, setDateTimeButton.offsetHeight);
+
+      // Make the date and time editable.
+      cr.webUIListenerCallback('can-set-date-time-changed', true);
+      assertGT(setDateTimeButton.offsetHeight, 0);
+
+      assertFalse(showSetDateTimeUICalled);
+      MockInteractions.tap(setDateTimeButton);
+      assertTrue(showSetDateTimeUICalled);
+
+      // Make the date and time not editable.
+      cr.webUIListenerCallback('can-set-date-time-changed', false);
+      assertEquals(setDateTimeButton.offsetHeight, 0);
+    });
   });
 })();