Fixed drop-down bug, for now

Expect it to break again in Chrome 54

rpg-docs/public/custom_components/paper-dropdown/paper-dropdown.html

@@ -40,6 +40,8 @@ Style the background color of the dropdown with these selectors:
 <link href="../../components/core-dropdown/core-dropdown.html" rel="import">
 <link href="../../components/paper-shadow/paper-shadow.html" rel="import">
 
+<link href="paper-dropdown-transition.html" rel="import">
+
 <style shim-shadowdom>
   html /deep/ paper-dropdown {
     position: absolute;
@@ -99,6 +101,9 @@ Style the background color of the dropdown with these selectors:
 <script>
 
   Polymer({
+    publish: { //Chrome 52 breaks this
+      transition: 'paper-dropdown-transition'
+    },
     ready: function() {
       this.super();
       this.sizingTarget = this.$.scroller;