function blobToArrayBuffer(blob) {
        return new Promise(function (resolve, reject) {
            var reader = new FileReader();
            reader.onloadend = function () {
                var result = reader.result || new ArrayBuffer(0);
                resolve(result);
            };
            reader.onerror = reject;
            reader.readAsArrayBuffer(blob);
        });
    }
Convert a <code>Blob</code> to an <code>ArrayBuffer</code>.

Example:

```js
blobUtil.blobToArrayBuffer(blob).then(function (arrayBuff) {
  // success
}).catch(function (err) {
  // error
});
```

@param blob
@returns Promise that resolves with the <code>ArrayBuffer</code>