InputStreamからBitmapへの変換でのエラー

画像をリクエストしているのですが、SkImageDecoder::Factory returned nullとなります。
statuscodeは200でした。
URLはhttps://outlook.office365.com/owa/service.svc/s/GetFileAttachment?id=HOGEHOGE.です。

try {
    HttpGet httpGet = new HttpGet(URL);
    CookieManager cookie = CookieManager.getInstance();
    String cookiestr = cookie.getCookie(URL);
    httpGet.setHeader("Cookie", cookiestr);
    DefaultHttpClient client = new DefaultHttpClient();

    HttpResponse httpResponse = client.execute(httpGet);
    int statusCode = httpResponse.getStatusLine().getStatusCode();
    Log.d("","statusCode:"+statusCode);
    HttpEntity entity = httpResponse.getEntity();
    //String response = EntityUtils.toString(entity);
    //Log.d("","response:"+response);
    BufferedHttpEntity bufferedEntity = new BufferedHttpEntity(entity);
    final InputStream in = bufferedEntity.getContent();

    Bitmap bitm = BitmapFactory.decodeStream(in); 
    entity.consumeContent();
    client.getConnectionManager().shutdown();
} catch (MalformedURLException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}