createObjectURLを使ったらrevokeObjectURLを呼ぶ ref: http://qiita.com/ykst/items/a367359cd4ee96cde802

example.js

function loadImage(array_buffer, onload) {
    var img = new Image();
    img.src = URL.createObjectURL(new Blob([array_buffer], {type:'image/jpeg'}));
    img.onload = function() {
        onload(img); // imgを即座に使い終わる関数
        URL.revokeObjectURL(img.src);
    };
}