jquery & google maps: loading page fragment including map asynchronous

See:http://stackoverflow.com/questions/14229695/google-maps-api-throws-uncaught-referenceerror-google-is-not-defined-only-whe/14235500#comment19769525_14235500

HTML

<script>
$(document).ready(function(e) {
    $('button').click(function(){
        $(this).hide();$('#a').html('Loading...');
        $.ajax({dataType:'html',
            type: 'POST', url: '/echo/html/',
           ...