Sanitize headers in Proxy Authentication Required responses

BUG=431504

Review URL: https://codereview.chromium.org/769043003

Cr-Commit-Position: refs/heads/master@{#310014}
bool IsTransportSocketPoolStalled(net::HttpNetworkSession* session) {
  return session->GetTransportSocketPool(
      net::HttpNetworkSession::NORMAL_SOCKET_POOL)->IsStalled();
}

bool IsTransportSocketPoolStalled(net::HttpNetworkSession* session) {
  return session->GetTransportSocketPool(
      net::HttpNetworkSession::NORMAL_SOCKET_POOL)->IsStalled();
}
