Response headers returned by Google's NaCL are incomplete

Response headers returned by Google's NaCL are incomplete. I can see in the network tab of chrome developer tools that browser actually received all the headers but NaCl is returning me incomplete headers in c++ code.

Headers i see in network tab of chrome:

HTTP/1.1 200 OK
Content-Type: application/octet-stream
Content-Length: 3312
Connection: keep-alive
Date: Wed, 14 Sep 2016 02:12:37 GMT
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET
Last-Modified: Wed, 14 Sep 2016 02:12:37 GMT
ETag: "644c53b76e0fd646aad2f4aaf313067d"
x-amz-version-id: rMFIbU5ptnyKgwn1_YRNr5OkEkTT8cEV
Accept-Ranges: bytes
Server: AmazonS3
Vary: Origin
X-Cache: Miss from cloudfront
Via: 1.1 a75bbd1dd9f3f983d073b0972494851d.cloudfront.net (CloudFront)
X-Amz-Cf-Id: 41xr_GlfJLkZ_SszRBmy62jCVjQgCl9sgyHtusJjc95Tb91BISksyg==

Headers i receive in c++ code from NaCL:

Content-Type: application/octet-stream
Last-Modified: Wed, 14 Sep 2016 02:12:37 GMT

This is how i access and print headers received form NaCL:

//Following is inside callback method passed to pp::URLLoader::Open method as second argument.

    auto response = _pLoader->GetResponseInfo();
    auto headers = response.GetHeaders().AsString();
    std::cout<< headers << std::endl;

Question: How can i get all the headers and print them?