title: google.maps.Marker zIndex doesn't work for two icon types - Symbol and String
body: <p>When I add more Markers to Google Map with different icon types like:</p>
  
  <pre><code>...
  var marker = new google.maps.Marker({
               position: markerLatLng,
               map: map,
               icon: "http://www.test.com/marker.png",
               zIndex: 10
           });
  ...
  </code></pre>
  
  <p>and</p>
  
  <pre><code>...
  var resultIcon = {
              path: google.maps.SymbolPath.CIRCLE,
              fillColor: "black",
              strokeColor: "black",
              strokeWeight: 1,
           };
  
  var marker = new google.maps.Marker({
               position: markerLatLng,
               map: map,
               icon: resultIcon,
               zIndex: 5
           });
  ...
  </code></pre>
  
  <p>Than the zIndex doesn't work and the Symbol marker appears on the top.</p>
  
  <p>Am I wrong with my code or how can I make the zIndex working?</p>