我需要画一个形状，然后添加阴影，但是阴影会覆盖填充颜色，我希望它在下面.. 我无法很好地解释情况，这里有一个在jsfiddle上的示例
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
context.beginPath();
context.moveTo(170, 80);
context.bezierCurveTo(130, 100, 130, 150, 230, 150);
context.bezierCurveTo(250, 180, 320, 180, 340, 150);
context.bezierCurveTo(420, 150, 420, 120, 390, 100);
context.bezierCurveTo(430, 40, 370, 30, 340, 50);
context.bezierCurveTo(320, 5, 250, 20, 250, 50);
context.bezierCurveTo(200, 5, 150, 20, 170, 80);
context.closePath();
context.lineWidth = 5;
context.fillStyle = "#8ED6FF";
context.strokeStyle = "#0000ff";
context.shadowColor = "#000000";
context.shadowBlur = 2;
context.shadowOffsetX = 5;
context.shadowOffsetY = 5;
context.fill();
context.stroke();