html2canvas/src/dummyimagecontainer.js

function DummyImageContainer(src) {
    this.src = src;
    log("DummyImageContainer for", src);
    if (!this.promise || !this.image) {
        log("Initiating DummyImageContainer");
        DummyImageContainer.prototype.image = new Image();
        var image = this.image;
        DummyImageContainer.prototype.promise = new Promise(function(resolve, reject) {
            image.onload = resolve;
            image.onerror = reject;
            image.src = smallImage();
            if (image.complete === true) {
                resolve(image);
            }
        });
    }
}