function base64StringToBlob(base64, type) {
        var parts = [binaryStringToArrayBuffer(atob(base64))];
        return type ? createBlob(parts, { type: type }) : createBlob(parts);
    }
Convert a base64-encoded string to a <code>Blob</code>.

Example:

```js
var blob = blobUtil.base64StringToBlob(base64String);
```
@param base64 - base64-encoded string
@param type - the content type (optional)
@returns Blob