CalculateFacesWithin = function (tileX, tileY, width, height, layer)
{
    var above = null;
    var below = null;
    var left = null;
    var right = null;

    var tiles = GetTilesWithin(tileX, tileY, width, height, null, layer);

    for (var i = 0; i < tiles.length; i++)
    {
        var tile = tiles[i];

        if (tile)
        {
            if (tile.collides)
            {
                above = GetTileAt(tile.x, tile.y - 1, true, layer);
                below = GetTileAt(tile.x, tile.y + 1, true, layer);
                left = GetTileAt(tile.x - 1, tile.y, true, layer);
                right = GetTileAt(tile.x + 1, tile.y, true, layer);

                tile.faceTop = (above && above.collides) ? false : true;
                tile.faceBottom = (below && below.collides) ? false : true;
                tile.faceLeft = (left && left.collides) ? false : true;
                tile.faceRight = (right && right.collides) ? false : true;
            }
            else
            {
                tile.resetFaces();
            }
        }
    }
}
Calculates interesting faces within the rectangular area specified (in tile coordinates) of the
layer. Interesting faces are used internally for optimizing collisions against tiles. This method
is mostly used internally.

@function Phaser.Tilemaps.Components.CalculateFacesWithin
@since 3.0.0

@param {number} tileX - The left most tile index (in tile coordinates) to use as the origin of the area.
@param {number} tileY - The top most tile index (in tile coordinates) to use as the origin of the area.
@param {number} width - How many tiles wide from the `tileX` index the area will be.
@param {number} height - How many tiles tall from the `tileY` index the area will be.
@param {Phaser.Tilemaps.LayerData} layer - The Tilemap Layer to act upon.