2.4.3 vivo平台截图问题

Cocos2d-x
#1

canvas使用toDataURL方法转成Base64出现空字符串问题，以下是主要代码：
private static getCanvas(data, width, height) {
var canvas = document.createElement(‘canvas’);
var ctx = canvas.getContext(‘2d’);
ctx.clearRect(0, 0, width, height);//清理之前的数据
canvas.width = width;
canvas.height = height;

    //优化截图效率：https://forum.cocos.com/t/2-1-3-4/72655
    //原生： https://forum.cocos.com/t/cocoscreator/72580/18
    let imageData = ctx.createImageData(width, height);
    // write the render data
    for (let i = 0; i < data.length; i++) {
        imageData.data[i] = data[i];
    }
    ctx.putImageData(imageData, 0, 0);
    return canvas;
}