fillLine(startX, startY, endX, endY) {
		this.strokeLine(startX, startY, endX, endY);
	}
Fill a line of the given two points
@param {number} startX - the start x coordinate
@param {number} startY - the start y coordinate
@param {number} endX - the end x coordinate
@param {number} endY - the end y coordinate