MD Bookmarks: Initial screenreader accessibility improvements

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/html/cr/ui/command.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/shared_style.html">
 <link rel="import" href="chrome://bookmarks/store_client.html">
 
 <dom-module id="bookmarks-command-manager">
   <template>
     <style include="shared-style">
       .label {
         flex: 1;
       }
 
       .sublabel {
         -webkit-margin-start: 8px;
         color: var(--secondary-text-color);
         text-align: end;
         width: 3ch;
       }
 
       :host(:not([has-any-sublabel_])) .sublabel {
         display: none;
       }
     </style>
     <template is="cr-lazy-render" id="dropdown">
-      <dialog is="cr-action-menu" on-mousedown="onMenuMousedown_">
+      <dialog is="cr-action-menu" on-mousedown="onMenuMousedown_" role="menu">
         <template is="dom-repeat" items="[[menuCommands_]]" as="command">
           <button class="dropdown-item"
               command$="[[command]]"
               hidden$="[[!isCommandVisible_(command, menuIds_)]]"
               disabled$="[[!isCommandEnabled_(command, menuIds_)]]"
-              on-tap="onCommandClick_">
+              on-tap="onCommandClick_"
+              role="menuitem">
             <span class="label">
               [[getCommandLabel_(command, menuIds_)]]
             </span>
             <span class="sublabel">
               [[getCommandSublabel_(command, menuIds_)]]
             </span>
           </button>
           <hr hidden$="[[!showDividerAfter_(command, menuIds_)]]"></hr>
         </template>
       </dialog>
@@ skipping 11 matching lines @@
           </paper-button>
           <paper-button class="action-button" on-tap="onOpenConfirmTap_">
             $i18n{openDialogConfirm}
           </paper-button>
         </div>
       </dialog>
     </template>
   </template>
   <script src="chrome://bookmarks/command_manager.js"></script>
 </dom-module>