title: Google Maps Drawing Manager limit to 1 polygon
body: <p>I am creating a map with the google maps v3 API.  Using the drawing manager to draw shapes.  Is there a way to disable the polygon button after 1 polygon has been drawn?  I been reading thru the API but can't find any events for polygon start, only for polygoncomplete.</p>
  
  <p>Maybe a way to detect drawingmode change? or remove <code>google.maps.drawing.OverlayType.POLYGON</code> but put it back if the current polygon was deleted?</p>