code: function getExtendedBounds(map, bounds, gridSize) {
    // Turn the bounds into latlng.
    var northEastLat = bounds && bounds.getNorthEast() && bounds.getNorthEast().lat;
    var northEastLng = bounds && bounds.getNorthEast() && bounds.getNorthEast().lng;
    var southWestLat = bounds && bounds.getSouthWest() && bounds.getSouthWest().lat;
    var southWestLng = bounds && bounds.getSouthWest() && bounds.getSouthWest().lng;
  
    var tr = _leaflet2.default.latLng(northEastLat, northEastLng);
    var bl = _leaflet2.default.latLng(southWestLat, southWestLng);
  
    // Convert the points to pixels and the extend out by the grid size.
    var trPix = map.latLngToLayerPoint(tr);
    trPix.x += gridSize;
    trPix.y -= gridSize;
  
    var blPix = map.latLngToLayerPoint(bl);
    blPix.x -= gridSize;
    blPix.y += gridSize;
  
    // Convert the pixel points back to LatLng
    var ne = map.layerPointToLatLng(trPix);
    var sw = map.layerPointToLatLng(blPix);
  
    // Extend the bounds to contain the new bounds.
    bounds.extend(ne);
    bounds.extend(sw);
  
    return bounds;
  }
docs: Taken from http://stackoverflow.com/questions/1538681/how-to-call-fromlatlngtodivpixel-in-google-maps-api-v3/12026134#12026134 and modified to use Leaflet API