Prevent updateOpenCommand() from receiving e.target of type other than BookmarkList|BookmarkTree

R=arv@chromium.org
BUG=393873

Review URL: https://codereview.chromium.org/594373002

Cr-Commit-Position: refs/heads/master@{#296456}

chrome/browser/resources/bookmark_manager/js/main.js

@@ -459,7 +459,7 @@ function handleCanExecuteForDocument(e) {
       e.canExecute = e.currentTarget.activeElement !== $('term');
       break;
     default:
-      canExecuteForList(e);
+      handleCanExecuteForList(e);
       break;
   }
 }