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

chrome/browser/resources/settings/date_time_page/date_time_page.html

 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="/controls/settings_checkbox.html">
 <link rel="import" href="/controls/settings_dropdown_menu.html">
 <link rel="import" href="/i18n_setup.html">
 <link rel="import" href="/prefs/prefs_behavior.html">
 <link rel="import" href="/prefs/prefs_types.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-date-time-page">
   <template>
     <style include="settings-shared">
       settings-dropdown-menu {
         --md-select-width: 400px;
       }
 
       cr-policy-pref-indicator {
         -webkit-margin-start: var(--checkbox-spacing);
       }
+
+      .hidden {
+        display: none;
+      }

[stevenjb, 2016/10/26 19:36:21]

Use hidden=[[!canSetDateTime_]] instead to be consistent with everywhere else?

[michaelpg, 2016/11/02 01:54:14]

Done.

     </style>
     <div class="settings-box first">
       <settings-dropdown-menu pref="{{prefs.cros.system.timezone}}"
           menu-options="[[timeZoneList_]]"
           disabled="[[timeZoneAutoDetect_]]">
       </settings-dropdown-menu>
     </div>
     <div class="settings-box continuation">
       <paper-checkbox
           id="timeZoneAutoDetectCheckbox"
           checked="[[timeZoneAutoDetect_]]"
           disabled="[[hasTimeZoneAutoDetectPolicy_]]"
           on-change="onTimeZoneAutoDetectCheckboxChange_">
         $i18n{timeZoneGeolocation}
       </paper-checkbox>
       <template is="dom-if" if="[[hasTimeZoneAutoDetectPolicy_]]">
         <cr-policy-pref-indicator pref="[[timeZonePolicyPref_]]">
         </cr-policy-pref-indicator>
       </template>
     </div>
     <div class="settings-box continuation">
       <settings-checkbox pref="{{prefs.settings.clock.use_24hour_clock}}"
           label="$i18n{use24HourClock}">
       </settings-checkbox>
     </div>
+    <div class="settings-box hidden" id="setDateTime" actionable
+        on-tap="onSetDateTimeTap_">
+      <div class="start"><div>$i18n{setDateTime}</div></div>

[stevenjb, 2016/10/26 19:36:21]

nit: This is hard to read, can we put this on 3 lines instead?

[michaelpg, 2016/11/02 01:54:14]

Done.

+      <button class="subpage-arrow" is="paper-icon-button-light"></button>
+    </div>
   </template>
   <script src="/date_time_page/date_time_page.js"></script>
 </dom-module>