// Add  10  markers to the map at random locations
         var bounds = map.getBoundsAsync(
         function(bounds)
         {
          var southWest = bounds.getSouthWest();
          var northEast = bounds.getNorthEast();
          var lngSpan = northEast.lng() - southWest.lng();
          var latSpan = northEast.lat() - southWest.lat();
         for (var i =  0 ; i <  10 ; i++)
         {
            var point = new GLatLng(southWest.lat() + latSpan * Math.random(),
                   southWest.lng() + lngSpan * Math.random());
            map.addOverlay(new GMarker(point));
    }
  });

  <button type="button" onclick="function(bounds)" - бред какой-то

Asynchronous Methods:        getBoundsAsync(callback)
Callback Value  :                  GLatLngBounds
Description:                         Returns the the visible rectangular region of the map view in geographical coordinates.