one-liners for a few polymer-related libraries

pkg/custom_element/lib/custom_element.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
- * Custom Elements let authors define their own elements. Authors associate code
- * with custom tag names, and then use those custom tag names as they would any
- * standard tag. See <www.polymer-project.org/platform/custom-elements.html>
- * for more information.
+ * Custom DOM elements.
+ *
+ * This library provides access to the Polymer project's
+ * [Custom Elements]
+ * (http://www.polymer-project.org/platform/custom-elements.html)
+ * API, which lets you define your own elements. With custom elements, you
+ * associate code with custom tag names, and then use those custom tag names
+ * as you would any standard tag. For more information, see the
+ * [Polymer.dart homepage](https://www.dartlang.org/polymer-dart/) and its
+ * [custom element example]
+ * (https://www.dartlang.org/polymer-dart/#custom-elements).
  */
 library custom_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:mdv/mdv.dart' as mdv;
 import 'package:meta/meta.dart';
 import 'src/custom_tag_name.dart';
 
 // TODO(jmesserly): replace with a real custom element polyfill.
@@ skipping 612 matching lines @@
       for (var removed in record.removedNodes) {
         if (identical(node, removed)) {
           observer.disconnect();
           element.removed();
           return;
         }
       }
     }
   }).observe(element.parentNode, childList: true);
 }