Display function signatures instead of just "Function".

client/lib/components/library.html

 <link rel="import" href="category.html">
 <link rel="import" href="class.html">
 <link rel="import" href="comment.html">
 <link rel="import" href="item.html">
 
 <polymer-element name="dartdoc-library" attributes="item">
   <template>
     <div class="page-header"><h1>{{item.decoratedName}} library</h1></div>
 
     <!-- Comment -->
     <!--  TODO(alanknight): The div with itemList and panel are here to
     convince it to use the right paragraph spacing. Seems pretty awful. -->
     <div id="itemList">
       <div is="dartdoc-comment" class="panel" item="{{item}}"></div>
     </div>
     <div class="accordion" id="accordion-grouping">
       <!-- Note: the implementation knows about the order of these items. -->
       <dartdoc-category category="{{item.operators}}"
           methods="{{lazyOperators}}"></dartdoc-category>
       <dartdoc-category category="{{item.variables}}"
           variables="{{lazyVariables}}"></dartdoc-category>
       <dartdoc-category category="{{item.functions}}"
           methods="{{lazyFunctions}}"></dartdoc-category>
       <dartdoc-category category="{{item.classes}}"
           items="{{lazyClasses}}"></dartdoc-category>
       <dartdoc-category category="{{item.typedefs}}"
-          items="{{lazyTypedefs}}"></dartdoc-category>
+          typedefs="{{lazyTypedefs}}"></dartdoc-category>
       <dartdoc-category category="{{item.errors}}"
           items="{{lazyErrors}}"></dartdoc-category>
     </div>
   </template>
 
   <script type="application/dart;component=1" src="library.dart"></script>
 </polymer-element>