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

chrome/browser/resources/settings/date_time_page/date_time_page.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'settings-date-time-page' is the settings page containing date and time
  * settings.
  */
 
@@ skipping 82 matching lines @@
 
   observers: [
     'maybeGetTimeZoneList_(' +
         'prefs.cros.system.timezone.value, timeZoneAutoDetect_)',
   ],
 
   attached: function() {
     this.addWebUIListener(
         'time-zone-auto-detect-policy',
         this.onTimeZoneAutoDetectPolicyChanged_.bind(this));
+    this.addWebUIListener(
+        'can-set-date-time-changed', this.onCanSetDateTimeChanged_.bind(this));
+
     chrome.send('dateTimePageReady');
-
     this.maybeGetTimeZoneList_();
   },
 
   /**
    * @param {boolean} managed Whether the auto-detect setting is controlled.
    * @param {boolean} valueFromPolicy The value of the auto-detect setting
    *     forced by policy.
    * @private
    */
   onTimeZoneAutoDetectPolicyChanged_: function(managed, valueFromPolicy) {
@@ skipping 12 matching lines @@
         key: 'fakeTimeZonePref',
         type: chrome.settingsPrivate.PrefType.NUMBER,
         value: 0,
         policySource: chrome.settingsPrivate.PolicySource.DEVICE_POLICY,
         policyEnforcement: chrome.settingsPrivate.PolicyEnforcement.ENFORCED,
       };
     }
   },
 
   /**
+   * @param {boolean} canSetDateTime Whether date and time are settable.
+   * @private
+   */
+  onCanSetDateTimeChanged_: function(canSetDateTime) {
+    this.$.setDateTime.classList.toggle('hidden', !canSetDateTime);
+  },
+
+  /**
    * @param {!Event} e
    * @private
    */
   onTimeZoneAutoDetectCheckboxChange_: function(e) {
     this.setPrefValue(
         'settings.resolve_timezone_by_geolocation', e.target.checked);
   },
 
+  /** @private */
+  onSetDateTimeTap_: function() {
+    chrome.send('showSetDateTimeUI');
+  },
+
   /**
    * @param {settings.TimeZoneAutoDetectPolicy} timeZoneAutoDetectPolicy
    * @return {boolean}
    * @private
    */
   computeHasTimeZoneAutoDetectPolicy_: function(timeZoneAutoDetectPolicy) {
     return timeZoneAutoDetectPolicy != settings.TimeZoneAutoDetectPolicy.NONE;
   },
 
   /**
@@ skipping 41 matching lines @@
    */
   setTimeZoneList_: function(timeZones) {
     this.timeZoneList_ = timeZones.map(function(timeZonePair) {
       return {
         name: timeZonePair[1],
         value: timeZonePair[0],
       };
     });
   },
 });