Move net.html import down into the modules that use it

Tools/GardeningServer/model/tree-status.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="../lib/net.html">
+
 <script>
 function TreeStatus(project) {
   this.project = project;
   this.message = '';
   this.status = 'unknown';
 
   this.url = "http://{1}-status.appspot.com/".assign(project);
 }
 
 TreeStatus.prototype.update = function() {
@@ skipping 14 matching lines @@
   var responseLowerCase = status.message.toLowerCase();
   if (responseLowerCase.indexOf('throttled') != -1) {
     this.status = 'throttled';
   } else if (responseLowerCase.indexOf("closed") != -1) {
     this.status = 'closed';
   } else {
     this.status = 'unknown';
   }
 };
 </script>