Move builderList creation to ct-failure-card

Tools/GardeningServer/ui/ct-builder-grid.html

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <link rel="import" href="../model/ct-builder.html">
 <link rel="import" href="../model/ct-builder-list.html">
 <link rel="import" href="ct-builder.html">
 
-<polymer-element name="ct-builder-grid" attributes="failures">
+<polymer-element name="ct-builder-grid" attributes="builderList">
   <template>
     <style>
       ct-builder {
         display: block;
       }
     </style>
-    <template repeat="{{ builder in _builderList.builders }}">
+    <template repeat="{{ builder in builderList.builders }}">
       <ct-builder builder="{{ builder }}"></ct-builder>
     </template>
   </template>
   <script>
     Polymer({
-      failures: null,
-      _builderList: null,
-
-      failuresChanged: function() {
-        this._builderList = new CTBuilderList(this.failures);
-      },
+      builderList: null,
     });
   </script>
 </polymer-element>