Make durations look nice on the task list

appengine/swarming/elements/res/imp/tasklist/task-list-data.html

Index: appengine/swarming/elements/res/imp/tasklist/task-list-data.html
diff --git a/appengine/swarming/elements/res/imp/tasklist/task-list-data.html b/appengine/swarming/elements/res/imp/tasklist/task-list-data.html
index d393ac7dbb64b3ba394627e8c0b77bd2778232a5..aceba1f3b9fb1d1932740f06502f0a75a9e962e7 100644
--- a/appengine/swarming/elements/res/imp/tasklist/task-list-data.html
+++ b/appengine/swarming/elements/res/imp/tasklist/task-list-data.html
@@ -237,7 +237,8 @@
         // 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 = (new Date()).toString();
+        var now = new Date();
+        var str = now.toString();
         var timeZone = str.substring(str.indexOf("("))
 
         // Do any preprocessing here
@@ -252,11 +253,19 @@
           t.tagMap = tagMap;
           TIMES.forEach(function(time) {
             if (t[time]) {
-              var d = new Date(t[time]);
-              var locale = d.toLocaleString();
+              t[time] = new Date(t[time]);
+              var locale = t[time].toLocaleString();
               t["human_"+time] = locale + " " + timeZone;
             }
           });
+          // Running tasks have no duration set, so we can figure it out.
+          if (!t.duration && t.state === "RUNNING" && t.started_ts){
+            t.duration = (now - t.started_ts) / 1000;
+          }
+          // Make the duration human readable
+          if (t.duration){
+            t.human_duration = sk.human.strDuration(t.duration);
+          }
         });
         return this._list.items;
       }