Hola Jose, te comparto otra version del codigo de barras, 
<canvas width="600" height="400"></canvas>
<script>
    function dibujarRectangulo(x, y, base, altura, color) {
        var pantalla = document.querySelector("canvas");
        var pincel = pantalla.getContext("2d");
        pincel.fillStyle=color;
        pincel.fillRect(x,y, base, altura);
        pincel.strokeStyle="black";
        pincel.strokeRect(x,y, base, altura);
    }
    function escribirTexto(x , y, texto) {
        var pantalla = document.querySelector("canvas");
        var pincel = pantalla.getContext("2d");
        pincel.font="15px Georgia";
        pincel.fillStyle="black";
        pincel.fillText(texto, x, y);    
    }
    var serie2009 = [6, 47, 41, 3, 3];
    var serie2019 = [81, 9, 3, 3, 4];
    var colores = ["blue","green","yellow", "red","gray"];
    var productos = ["Chrome", "Firefox", "IE/Edge", "Safari", "Otros"];
    var xInicial1 =  100;
    var xInicial2 =  400;
    var yInicial1 = 190;
    var yInicial2 = 190;
    var base = 100;
    dibujarRectangulo(10,10,580,380,"white");
    for(var i = 0; i < 5; i++) {
        dibujarRectangulo(xInicial1, yInicial1, base, serie2009[i]*2, colores[i]);
        dibujarRectangulo(xInicial2, yInicial2, base, serie2019[i]*2, colores[i]);
        yInicial1 += serie2009[i]*2;
        yInicial2 += serie2019[i]*2; 
    }
    // Leyendas
    for(var i = 0; i < 5; i++) {
       dibujarRectangulo(30 + (100*i), 40, 20, 20, colores[i]);
       escribirTexto(30 + (100*i),80, productos[i]);
    }   
    // Titulos Barras
    escribirTexto(135,170, "2009");
    escribirTexto(435,170, "2019");
</script>