MD Extensions: Show messages for no extensions, and for no search results

chrome/browser/resources/md_extensions/manager.html

 <link rel="import" href="chrome://resources/cr_elements/cr_drawer/cr_drawer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/promise_resolver.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-header-panel/paper-header-panel.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animated-pages.html">
@@ skipping 71 matching lines @@
       </extensions-toolbar>
       <dialog id="drawer" is="cr-drawer" heading="$i18n{toolbarTitle}">
         <div class="drawer-content">
           <extensions-sidebar></extensions-sidebar>
         </div>
       </dialog>
       <neon-animated-pages id="pages" attr-for-selected="id"
           selected="items-list">
         <extensions-item-list id="items-list" items="[[extensions]]"
             delegate="[[itemDelegate]]" in-dev-mode="[[inDevMode]]"
-            filter="[[filter]]"
-            hidden$="[[computeListHidden_(extensions, extensions.splices, apps, apps.splices)]]">
+            filter="[[filter]]" hidden$="[[!didInitPage_]]">
         </extensions-item-list>
         <extensions-detail-view id="details-view" delegate="[[itemDelegate]]"
             in-dev-mode="[[inDevMode]]" data="[[detailViewItem_]]"
             on-close="onDetailsViewClose_">
         </extensions-detail-view>
         <extensions-keyboard-shortcuts id="keyboard-shortcuts"
             items="[[extensions]]">
         </extensions-keyboard-shortcuts>
         <extensions-error-page id="error-page" on-close="onErrorPageClose_"
             data="[[errorPageItem_]]">
         </extensions-error-page>
       </neon-animated-pages>
       <extensions-options-dialog id="options-dialog">
       </extensions-options-dialog>
       <extensions-pack-dialog id="pack-dialog"></extensions-pack-dialog>
       <extensions-load-error id="load-error"></extensions-load-error>
     </paper-header-panel>
   </template>
   <script src="chrome://extensions/manager.js"></script>
 </dom-module>