code: public static BoundingBox getProjectedBoundingBox(Projection projection,
  			TileGrid tileGrid, int zoom) {
  
  		BoundingBox boundingBox = getWebMercatorBoundingBox(tileGrid, zoom);
  
  		if (projection != null) {
  			ProjectionTransform transform = webMercator
  					.getTransformation(projection);
  			boundingBox = boundingBox.transform(transform);
  		}
  
  		return boundingBox;
  	}
docs: Get the Projected tile bounding box from the Google Maps API tile grid
  and zoom level
  
  @param projection
  projection
  @param tileGrid
  tile grid
  @param zoom
  zoom level
  @return bounding box