Update from https://crrev.com/306655

net/quic/crypto/p256_key_exchange_nss.cc

 // Copyright (c) 2013 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.
 
 #include "net/quic/crypto/p256_key_exchange.h"
 
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/sys_byteorder.h"
 
 using base::StringPiece;
 using std::string;
 using std::vector;
 
 namespace net {
 
 namespace {
 
@@ skipping 106 matching lines @@
   // NSS lacks the ability to import an ECC private key without
   // also importing the public key, so it is necessary to also
   // store the public key.
   vector<uint8> public_key;
   if (!key_pair->ExportPublicKey(&public_key)) {
     DVLOG(1) << "Can't export public key.";
     return string();
   }
 
   // TODO(thaidn): determine how large encrypted private key can be
-  uint16 private_key_size = private_key.size();
+  uint16 private_key_size = base::checked_cast<uint16>(private_key.size());
   const size_t result_size = sizeof(private_key_size) +
                              private_key_size +
                              public_key.size();
   vector<char> result(result_size);
   char* resultp = &result[0];
   // Export the key string.
   // The first two bytes are the private key's size in little endian.
   private_key_size = base::ByteSwapToLE16(private_key_size);
   memcpy(resultp, &private_key_size, sizeof(private_key_size));
   resultp += sizeof(private_key_size);
@@ skipping 78 matching lines @@
 }
 
 StringPiece P256KeyExchange::public_value() const {
   return StringPiece(reinterpret_cast<const char*>(public_key_),
                      sizeof(public_key_));
 }
 
 QuicTag P256KeyExchange::tag() const { return kP256; }
 
 }  // namespace net