app/views/layouts/doorkeeper/application.html.erb
<!DOCTYPE html>
<html>
<head>
<title><%= t('doorkeeper.layouts.application.title') %></title>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<%= stylesheet_link_tag "doorkeeper/application" %>
<%= csrf_meta_tags %>
</head>
<body>
<div id="container">
<%- if flash[:notice].present? %>
<div class="alert alert-info">
<%= flash[:notice] %>
</div>
<% end -%>
<%= yield %>
</div>
</body>
</html>