Google Maps Marker change size

HTML

<script src="http://maps.google.com/maps/api/js?sensor=false&amp;.js"></script>
<div id="map_canvas"></div>

CSS

#map_canvas{
    width: 450px;
    height: 400px;
}

JavaScript

function initialize() {
  var myOptions = {
    zoom: 10,
    center: new google.maps.LatLng(-33.9, 151.2),
    mapTypeId: google.maps.MapTypeId.ROADMAP
  }
  var map = new google.maps.Map(document.getElementById("map_canvas"),
                                myOptions);

  setMarker(map);
}

function setMarker(map){
    var beachFlagUrl = "https://image.flaticon.com/icons/svg/33/33622.svg";
    var beachflagShadowUrl = "https://image.flaticon.com/icons/svg/33/33622.svg";

    // Origins, anchor positions and coordinates of the marker
    // increase in the X direction to the right and in
    // the Y direction down.
    var image = new google.maps.MarkerImage(
      beachFlagUrl,
      // This marker is 20 pixels wide by 32 pixels tall.
      new google.maps.Size(20, 32),
      // The origin for this image is 0,0.
      new google.maps.Point(0,0),
      // The anchor for this image is the base of the flagpole at 0,32.
      new google.maps.Point(0, 32));
    var shadow = new google.maps.MarkerImage(
      beachflagShadowUrl,
      // The shadow image is larger in the horizontal dimension
      // while the position and offset are the same as for the main image.
      new google.maps.Size(37, 32),
      new google.maps.Point(0,0),
      new google.maps.Point(0, 32));
      
    var marker = new google.maps.Marker({
        position: new google.maps.LatLng(-33.9, 151.2),
        map: map,
        shadow: shadow,
        icon: image, 
        title: "Test Marker"
    });
    
google.maps.event.addListener(marker, 'mousedown', function() {             
              
        var newIcon = new google.maps.MarkerImage(
            this.icon.url, 
            new google.maps.Size(this.icon.size.width * 2,this.icon.size.height * 2 ), 
            this.icon.origin, 
            new google.maps.Point(0, 64), 
            new google.maps.Size(this.icon.size.width * 2,this.icon.size.height * 2 )
        );
        var newShadow = new google.maps.MarkerImage(
           ...