Fix Swarming UI timezone bug

appengine/swarming/ui/res/imp/tasklist/task-list-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-list-data>
 
@@ skipping 232 matching lines @@
           t.tags = t.tags || [];
           t.tags.forEach(function(tag) {
             var split = tag.split(":", 1)
             var key = split[0];
             var rest = tag.substring(key.length + 1);
             tagMap[key] = rest;
           });
           t.tagMap = tagMap;
 
           TIMES.forEach(function(time) {
-            if (t[time]) {
-              t[time] = new Date(t[time]);
-              t["human_"+time] = sk.human.localeTime(t[time]);
-            }
+            swarming.sanitizeAndHumanizeTime(t, time);
           });
           // Running tasks have no duration set, so we can figure it out.
           if (!t.duration && t.state === this.RUNNING && t.started_ts){
             t.duration = (now - t.started_ts) / 1000;
           }
           // Make the duration human readable
           if (t.duration){
             t.human_duration = this._humanDuration(t.duration);
           }
         }.bind(this));
         return json.items;
       }
     });
   })();
   </script>
 </dom-module>