ChromeOS: implement per-user time zone preferences.

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/cr_elements/policy/cr_policy_indicator.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="../controls/settings_dropdown_menu.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../prefs/prefs_behavior.html">
@@ skipping 13 matching lines @@
 
       paper-toggle-button,
       cr-policy-indicator {
         -webkit-margin-start: var(--settings-control-spacing);
       }
     </style>
     <div class="settings-box first">
       <div id="timezoneGeolocateToggleLabel" class="start">
         $i18n{timeZoneGeolocation}
       </div>
-      <template is="dom-if" if="[[hasTimeZoneAutoDetectPolicy_]]" restamp>
-        <cr-policy-indicator indicator-type="devicePolicy"
-            icon-aria-label="$i18n{timeZoneGeolocation}">
-        </cr-policy-indicator>
-      </template>
-      <paper-toggle-button
+      <settings-toggle-button
+          pref="{{prefs.settings.resolve_timezone_by_geolocation}}"
           id="timeZoneAutoDetect"
-          aria-labelledby="timezoneGeolocateToggleLabel"
-          checked="[[timeZoneAutoDetect_]]"
-          disabled="[[hasTimeZoneAutoDetectPolicy_]]"
-          on-change="onTimeZoneAutoDetectChange_">
-      </paper-toggle-button>
+          aria-labelledby="timezoneGeolocateToggleLabel">
+      </settings-toggle-button>
     </div>
     <div class="settings-box continuation embedded">
-      <settings-dropdown-menu pref="{{prefs.cros.system.timezone}}"
+      <settings-dropdown-menu id="userTimeZoneSelector"
+          pref="{{prefs.settings.timezone}}"
           label="$i18n{timeZone}"
           menu-options="[[timeZoneList_]]"
-          disabled="[[timeZoneAutoDetect_]]">
+          hidden="[[isUserTimeZoneSelectorHidden_(prefs.settings.timezone,
+              prefs.settings.resolve_timezone_by_geolocation.value)]]">
+      </settings-dropdown-menu>
+      <settings-dropdown-menu id="systemTimezoneSelector"
+          pref="{{prefs.cros.system.timezone}}"
+          label="$i18n{timeZone}"
+          menu-options="[[timeZoneList_]]"
+          disabled
+          hidden="[[!isUserTimeZoneSelectorHidden_(prefs.settings.timezone,
+              prefs.settings.resolve_timezone_by_geolocation.value)]]">
       </settings-dropdown-menu>

[stevenjb, 2017/05/16 17:16:57]

Good point. You could create a fake pref and map that to the correct pref, but
that is probably more hassle then it is worth.

Instead, I would suggest using dom-if instead of hidden, it will make the fact
that we only show one or the other dropdown a bit more clear.

[Alexander Alekseev, 2017/05/19 11:25:29]

Done.

     </div>
     <div class="settings-box">
       <settings-toggle-button class="start"
           pref="{{prefs.settings.clock.use_24hour_clock}}"
           label="$i18n{use24HourClock}">
       </settings-toggle-button>
     </div>
     <div class="settings-box" id="setDateTime" actionable
         on-tap="onSetDateTimeTap_" hidden$="[[!canSetDateTime_]]">
       <div class="start">$i18n{setDateTime}</div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{setDateTime}"></button>
     </div>
   </template>
   <script src="date_time_page.js"></script>
 </dom-module>