title: Google Maps api - drawing library fill polygon before closing shape
body: <p>I have a google map and I am using the drawing library to let the user draw polygons on the map by clicking to add points.
  As a comparison I looked at trulia.com. I don't know how the drawing library setup is being made on trulia (uses backbone and other stuff). While I draw a shape, I want it to get filled as soon as I have 3 points, even if I am still drawing, and the fill should change as I add new points (indicating what the shape/area would be if you'd close it in that moment).</p>
  
  <p>On trulia.com, as soon as you have a 3rd point, the area designated by the existing points gets filled, even though you haven't finished adding points. They're using google maps api, right? But I can't find the setting for something like "fill shape as you add points". I've searched google a lot, no luck.</p>
  
  <p>Does anyone know how to setup the map or the drawing library to have that behavior? I don't think that this behavior can be setup in the polygonOptions (I've looked at all the options documented on developers.google.com)... so, the setting must be somewhere else...</p>