CenterOn = function (line, x, y)
{
    var tx = x - ((line.x1 + line.x2) / 2);
    var ty = y - ((line.y1 + line.y2) / 2);

    line.x1 += tx;
    line.y1 += ty;

    line.x2 += tx;
    line.y2 += ty;

    return line;
}
Center a line on the given coordinates.

@function Phaser.Geom.Line.CenterOn
@since 3.0.0

@param {Phaser.Geom.Line} line - The line to center.
@param {number} x - The horizontal coordinate to center the line on.
@param {number} y - The vertical coordinate to center the line on.

@return {Phaser.Geom.Line} The centered line.