Fix Swarming UI timezone bug

appengine/swarming/ui/res/imp/botpage/bot-page-data.html

 <!--
   Copyright 2016 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <bot-page-data>
 
@@ skipping 40 matching lines @@
   (function(){
     // Time to wait before requesting a new bot. This is to allow a user to
     // type in a name and not have it make one set of requests for each
     // keystroke.
     var BOT_ID_DEBOUNCE_MS = 400;
     var lastRequest;
 
     var BOT_TIMES = ["first_seen_ts", "last_seen_ts", "lease_expiration_ts"];
     var TASK_TIMES = ["started_ts", "completed_ts", "abandoned_ts", "modified_ts"];
 
-    var timezone;
-    function formatDate(date) {
-      if (!timezone) {
-        // Date.toString() looks like "Mon Aug 29 2016 09:03:41 GMT-0400 (EDT)"
-        // we want to extract the time zone part and append it to the
-        // locale time.
-        var str = date.toString();
-        timezone = str.substring(str.indexOf("("));
-      }
-      return date.toLocaleString() + " " + timezone;
-    }
-
     Polymer({
       is: 'bot-page-data',
 
       behaviors: [
           SwarmingBehaviors.BotPageBehavior,
       ],
 
       properties: {
         // inputs
         auth_headers: {
@@ skipping 94 matching lines @@
         bot.dimensions = bot.dimensions || [];
         bot.dimensions.forEach(function(dim) {
           if (swarming.alias.DIMENSIONS_WITH_ALIASES.indexOf(dim.key) !== -1) {
             dim.value.forEach(function(value, i){
               dim.value[i] = swarming.alias.apply(value, dim.key);
             });
           }
         });
 
         BOT_TIMES.forEach(function(time) {
-          if (bot[time]) {
-            bot[time] = new Date(bot[time]);
-            bot["human_"+time] = formatDate(bot[time]);
-          }
+          swarming.sanitizeAndHumanizeTime(bot, time);
         });
         return bot;
       },
 
       parseEvents: function(events) {
         if (!events || !events.items) {
           return [];
         }
         var events = events.items;
         events.forEach(function(event){
           // Do any preprocessing here
-          if (event.ts) {
-            event.ts = new Date(event.ts);
-            event.human_ts = formatDate(event.ts);
-          }
+          swarming.sanitizeAndHumanizeTime(event, "ts");
         });
 
         // Sort the most recent events first.
         events.sort(function(a,b) {
           return b.ts - a.ts;
         });
 
         return events;
       },
 
       parseTasks: function(tasks) {
         if (!tasks || !tasks.items) {
           return [];
         }
         var tasks = tasks.items;
 
         tasks.forEach(function(task){
           // Do any preprocessing here
           TASK_TIMES.forEach(function(time) {
-            if (task[time]) {
-              task[time] = new Date(task[time]);
-              task["human_"+time] = formatDate(task[time]);
-            }
+            swarming.sanitizeAndHumanizeTime(task, time);
           });
 
           if (task.duration) {
             task.human_duration = this._humanDuration(task.duration);
           } else {
             var end = task.completed_ts || task.abandoned_ts || task.modified_ts || new Date();
             task.human_duration = this._timeDiffExact(task.started_ts, end);
             task.duration = (end.getTime() - task.started_ts) / 1000;
           }
 
@@ skipping 13 matching lines @@
           return b.started_ts - a.started_ts;
         });
 
         return tasks;
       }
 
     });
   })();
   </script>
 </dom-module>