Показывать экран загрузки до тех пор, пока стиль маркеров данных geojson не будет установлен с помощью карт Google

#map {
  height: 100%;
}

html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

#loaddiv {
  BORDER-RIGHT: #785e4f 4px groove;
  PADDING-RIGHT: 20px;
  BORDER-TOP: #785e4f 4px groove;
  PADDING-LEFT: 20px;
  FONT-WEIGHT: bold;
  Z-INDEX: 100;
  FILTER: alpha(opacity=75);
  LEFT: 260px;
  PADDING-BOTTOM: 20px;
  MARGIN-LEFT: auto;
  BORDER-LEFT: #785e4f 4px groove;
  WIDTH: 250px;
  MARGIN-RIGHT: auto;
  PADDING-TOP: 20px;
  BORDER-BOTTOM: #785e4f 4px groove;
  POSITION: absolute;
  TOP: 150px;
  BACKGROUND-COLOR: #FFFFFF;
  /* BACKGROUND-COLOR: #e7b047; */
  TEXT-ALIGN: center;
  opacity: .75
}

<div id = "loaddiv">Loading.....&#160;&#160;&#160; please wait!<br /></div>
<div id = "map"></div>


<script async defer src = "https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initMap">
</script>
<script type = "text/javascript">
  var map;
  var featuresToBeStyled;
  var initialLoad = performance.now();

  function initMap() {
    map = new google.maps.Map(document.getElementById('map'), {
      zoom: 3,
      center: {
        lat: -1.54108,
        lng: 37.759902
      }
    });
    // NOTE: This uses cross-domain XHR, and may not work on older browsers.
    map.data.loadGeoJson('https://api.myjson.com/bins/bdmco', {}, function(features) {
      console.info("loadGeoJson complete, " + features.length + " features");
      featuresToBeStyled = features.length;
    });
    map.data.setStyle(styleFeature); //just once this is done I would like to show the map. Until it is not, I would like to show a loading screen
  }
  var iconsLoaded = 0;

  function styleFeature(feature) {
    var img = new Image();
    img.onload = (function(feature) {
      return function() {
        var timeImage = performance.now();
        iconsLoaded++;
        if (iconsLoaded == featuresToBeStyled)
          document.getElementById('loaddiv').style.display = "none";
      }
    })(feature);
    img.src = feature.getProperty('icon');
    var icon = {
      url: feature.getProperty('icon'),
      scaledSize: new google.maps.Size(30, 30),
      origin: new google.maps.Point(0, 0),
      anchor: new google.maps.Point(0, 30)
    };
    var amenity = feature.getProperty('amenity');
    return {
      icon: icon,
      title: amenity,
      visible: true,
    }
  }
</script>