ChromeOS: implement per-user time zone preferences.

chrome/browser/resources/options/browser_options.html

 <if expr="chromeos">
 <link rel="import" href="/people_page/lock_screen_constants.html">
 </if>
 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
   <include src="automatic_settings_reset_banner.html">
 <if expr="chromeos">
   <link rel="import" href="chrome://resources/cr_elements/chromeos/network/cr_network_icon.html">
@@ skipping 307 matching lines @@
   <section id="date-time-section">
     <h3 i18n-content="datetimeTitle"></h3>
     <div class="option-control-table">
       <div guest-visibility="disabled">
         <span id="timezone-value-label" class="option-name"
             i18n-content="timezone"></span>
         <div id="timezone-value">
           <select class="control"
               id="timezone-value-select"
               i18n-options="timezoneList" data-type="string"
-              pref="cros.system.timezone"
+              pref="settings.timezone"
               aria-labelledby="timezone-value-label"
               metric="Options_TimezoneSelect"></select>
         </div>
       </div>
       <div class="checkbox settings-row">
         <div id="resolve-timezone-by-geolocation-selection" hidden>
           <label>
             <input id="resolve-timezone-by-geolocation"
                 pref="settings.resolve_timezone_by_geolocation"
                 metric="Options_ResolveTimezoneByGeoLocation" type="checkbox">
@@ skipping 796 matching lines @@
       </button>
     </div>
   </section>
   </div>  <!-- advanced-settings-container -->
   </div>  <!-- advanced-settings -->
   <footer id="advanced-settings-footer">
     <a is="action-link" id="advanced-settings-expander"
         i18n-content="showAdvancedSettings"></a>
   </footer>
 </div>