MD Downloads: fix up some Polymer 1.2.3 issues and re-vulcanize

chrome/browser/resources/md_downloads/manager.html

 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/cr/ui.html">
 <link rel="import" href="chrome://resources/html/cr/ui/command.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-header-panel/paper-header-panel.html">
 <link rel="import" href="chrome://downloads/action_service.html">
 <link rel="import" href="chrome://downloads/constants.html">
 <link rel="import" href="chrome://downloads/i18n_setup.html">
 <link rel="import" href="chrome://downloads/item.html">
 <link rel="import" href="chrome://downloads/toolbar.html">
 
 <dom-module id="downloads-manager">
   <template>
-    <paper-header-panel id="panel" class="loading">
-      <downloads-toolbar class="paper-header" id="toolbar"></downloads-toolbar>
-      <iron-list id="downloads-list" items="{{items_}}"
-          hidden="[[!hasDownloads_]]">
-        <template>
-          <downloads-item data="[[item]]" hide-date="[[item.hideDate]]">
-          </downloads-item>
-        </template>
-      </iron-list>
-      <div id="no-downloads" hidden="[[hasDownloads_]]">
-        <div>
-          <div class="illustration"></div>
-          <span><!-- Text populated in Manager#updateAll_(). --></span>
-        </div>
+    <downloads-toolbar id="toolbar"></downloads-toolbar>
+    <iron-list id="downloads-list" items="{{items_}}"
+        hidden="[[!hasDownloads_]]">
+      <template>
+        <downloads-item data="[[item]]" hide-date="[[item.hideDate]]">
+        </downloads-item>
+      </template>
+    </iron-list>
+    <div id="no-downloads" hidden="[[hasDownloads_]]">
+      <div>
+        <div class="illustration"></div>
+        <span><!-- Text populated in Manager#updateAll_(). --></span>
       </div>
-    </paper-header-panel>
+    </div>
   </template>
   <link rel="import" type="css" href="chrome://downloads/shared_style.css">
   <link rel="import" type="css" href="chrome://downloads/manager.css">
   <script src="chrome://downloads/manager.js"></script>
 </dom-module>