title: Toogle Cesium requestRenderMode after Cesium.viewer has been created
body: <p>i am trying to toggle Cesiums viewer.requestRenderMode setting, to explore some performance differences. 
  I created a toggle Button for the requestRenderMode property and call the following function:</p>
  
  <pre><code>function toggleRenderMode() {
      console.info("toggleRenderMode");
      requestRenderMode = !requestRenderMode;
      viewer.requestRenderMode = requestRenderMode
      if(requestRenderMode){
          viewer.maximumRenderTimeChange = Infinity;
          console.info("enabling requestRenderMode");
  
      }else{
          viewer.maximumRenderTimeChange = 0;
          console.info("disabling requestRenderMode");
  
      }
      console.info("viewer.requestRenderMode:",viewer.requestRenderMode);
  </code></pre>
  
  <p>}</p>
  
  <p>the console output shows me that the viewers requestRenderMode is set according to the code, however it seems that this has no effect on the rendering. 
  So can this property only be set at the time of Cesium viewers creation? </p>
  
  <p>Thanks a lot!</p>