moodle/message/templates/message_area.mustache

<div class="messaging-area-all" data-loggedinuserid="{{loggedinuserid}}" data-userid="{{userid}}">
    <div class="actions">
        <ul title="{{#str}}edit{{/str}}" class="messagingareaactions">
            <li>
                <a href="#">{{#pix}}i/settings{{/pix}}</a>
                <ul class="dropdown-menu">
                    <li>
                        <a data-action="delete-messages" href="#">
                            {{#str}}delete{{/str}}
                        </a>
                    </li>
                </ul>
            </li>
        </ul>
    </div>
    <div class="messaging-area">
        <div class="row-fluid">
            <div class="span3 contacts-area" data-region="contacts-area">
                {{#contacts}}
                    {{> core_message/message_area_contacts_area }}
                {{/contacts}}
            </div>
            <div class="span9 messages-area" data-region="messages-area">
                {{#messages}}
                    {{> core_message/message_area_messages_area }}
                {{/messages}}
            </div>
        </div>
    </div>
</div>
{{#js}}
    require(['core_message/message_area', 'core_message/message_area_menubar', 'core_message/message_area_actions'],
        function(Messagearea, Menubar, Actions) {
            var messageArea = new Messagearea('.messaging-area-all');
            var actions = new Actions(messageArea);

            Menubar.enhance('.messagingareaactions', {
                "[data-action='delete-messages']": actions.chooseMessagesToDelete.bind(actions),
            });
        }
    );
{{/js}}