Introduce new bot-page UI

appengine/swarming/elements/res/imp/common/common-behavior.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.
 
   It contains the definition of the following Behaviors:
 
     SwarmingBehaviors.CommonBehavior
 
   To use it, include
@@ skipping 21 matching lines @@
       // because computed values in Polymer don't fire if a property is
       // undefined. Clients should check that bindTo is not falsey.
        _getJsonAsync: function(bindTo, url, busy, headers, params) {
         if (!bindTo || !url) {
           console.log("Need at least a polymer element to bind to and a url");
           return;
         }
         if (busy) {
           this.set(busy, true);
         }
-        url = url + "?" + sk.query.fromParamSet(params);
+        if (params) {
+          url = url + "?" + sk.query.fromParamSet(params);
+        }
         sk.request("GET", url, "", headers).then(JSON.parse).then(function(json){
           this.set(bindTo, json);
           if (busy) {
             this.set(busy, false);
           }
         }.bind(this)).catch(function(reason){
           console.log("Reason for failure of request to " + url, reason);
           this.set(bindTo, false);
           if (busy) {
             this.set(busy, false);
           }
         }.bind(this));
       },
 
       _not: function(a) {
         return !a;
       },
 
       _or: function() {
         var result = false;
         // can't use .foreach, as arguments isn't really an Array.
         for (var i = 0; i < arguments.length; i++) {
           result = result || arguments[i];
         }
         return result;
       },
     };
   })();
 </script>