Fix BoringSSL build and tests on OS X.

net/socket/ssl_client_socket_openssl.cc

 // Copyright (c) 2012 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.
 
 // OpenSSL binding for SSLClientSocket. The class layout and general principle
 // of operation is derived from SSLClientSocketNSS.
 
 #include "net/socket/ssl_client_socket_openssl.h"
 
 #include <errno.h>
@@ skipping 279 matching lines @@
   openssl_chain_.reset(NULL);
   os_chain_ = NULL;
 
   if (!chain)
     return;
 
   // sk_X509_dup does not increase reference count on the certs in the stack.
   openssl_chain_.reset(sk_X509_dup(chain));
 
   std::vector<base::StringPiece> der_chain;
-  for (int i = 0; i < sk_X509_num(openssl_chain_.get()); ++i) {
+  for (size_t i = 0; i < sk_X509_num(openssl_chain_.get()); ++i) {
     X509* x = sk_X509_value(openssl_chain_.get(), i);
 
     // Increase the reference count for the certs in openssl_chain_.
     CRYPTO_add(&x->references, 1, CRYPTO_LOCK_X509);
 
     unsigned char* cert_data = NULL;
     int cert_data_length = i2d_X509(x, &cert_data);
     if (cert_data_length && cert_data)
       der_chain.push_back(base::StringPiece(reinterpret_cast<char*>(cert_data),
                                             cert_data_length));
@@ skipping 1195 matching lines @@
   return socket->MaybeReplayTransportError(
       bio, cmd, argp, argi, argl, retvalue);
 }
 
 scoped_refptr<X509Certificate>
 SSLClientSocketOpenSSL::GetUnverifiedServerCertificateChain() const {
   return server_cert_;
 }
 
 }  // namespace net