MD Bookmarks: Add keyboard shortcut support to bookmarks-command-manager

chrome/browser/resources/md_bookmarks/command_manager.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
 <link rel="import" href="chrome://bookmarks/edit_dialog.html">
 <link rel="import" href="chrome://bookmarks/store_client.html">
 
 <dom-module id="bookmarks-command-manager">
   <template>
     <dialog is="cr-action-menu" id="dropdown" on-mousedown="onMenuMousedown_">
       <button class="dropdown-item"
           command="edit"
           hidden$="[[!canExecute('edit', menuIds_)]]"
           on-tap="onCommandClick_">
@@ skipping 11 matching lines @@
           on-tap="onCommandClick_">
         $i18n{menuDelete}
       </button>
     </dialog>
     <template is="cr-lazy-render" id="editDialog">
       <bookmarks-edit-dialog></bookmarks-edit-dialog>
     </template>
   </template>
   <script src="chrome://bookmarks/command_manager.js"></script>
 </dom-module>