Add OpenSSL BIO method that writes to a std::string.

crypto/crypto.gypi

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     # Put all transitive dependencies for Windows HMAC here.
     # This is required so that we can build them for nacl win64.
     'variables': {
       'hmac_win64_related_sources': [
@@ skipping 50 matching lines @@
       'mock_apple_keychain.cc',
       'mock_apple_keychain.h',
       'mock_apple_keychain_ios.cc',
       'mock_apple_keychain_mac.cc',
       'p224_spake.cc',
       'p224_spake.h',
       'nss_crypto_module_delegate.h',
       'nss_util.cc',
       'nss_util.h',
       'nss_util_internal.h',
+      'openssl_bio_string.cc',
+      'openssl_bio_string.h',
       'openssl_util.cc',
       'openssl_util.h',
       'p224.cc',
       'p224.h',
       'random.h',
       'random.cc',
       'rsa_private_key.cc',
       'rsa_private_key.h',
       'rsa_private_key_nss.cc',
       'rsa_private_key_openssl.cc',
@@ skipping 12 matching lines @@
       'signature_verifier_openssl.cc',
       'symmetric_key_nss.cc',
       'symmetric_key_openssl.cc',
       'third_party/nss/chromium-nss.h',
       'third_party/nss/pk11akey.cc',
       'third_party/nss/rsawrapr.c',
       'third_party/nss/secsign.cc',
     ]
   }
 }