Remove disabling of C4267 in 64-bit gn builds

components/gcm_driver/crypto/gcm_message_cryptographer.cc

 // Copyright 2015 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 "components/gcm_driver/crypto/gcm_message_cryptographer.h"
 
 #include <algorithm>
 #include <sstream>
 
 #include "base/logging.h"
@@ skipping 36 matching lines @@
 
   std::stringstream info_stream;
   info_stream << "Content-Encoding: " << content_encoding << '\x00';
 
   switch (label) {
     case GCMMessageCryptographer::Label::P256:
       info_stream << "P-256" << '\x00';
       break;
   }
 
-  uint16_t local_len = base::HostToNet16(recipient_public_key.size());
+  uint16_t local_len =
+      base::HostToNet16(static_cast<uint16_t>(recipient_public_key.size()));
   info_stream.write(reinterpret_cast<char*>(&local_len), sizeof(local_len));
   info_stream << recipient_public_key;
 
-  uint16_t peer_len = base::HostToNet16(sender_public_key.size());
+  uint16_t peer_len =
+      base::HostToNet16(static_cast<uint16_t>(sender_public_key.size()));
   info_stream.write(reinterpret_cast<char*>(&peer_len), sizeof(peer_len));
   info_stream << sender_public_key;
 
   return info_stream.str();
 }
 
 }  // namespace
 
 const size_t GCMMessageCryptographer::kAuthenticationTagBytes = 16;
 const size_t GCMMessageCryptographer::kSaltSize = 16;
@@ skipping 157 matching lines @@
                     0   /* subkey_secret_bytes_to_generate */);
 
   // draft-thomson-http-encryption defines that the result should be XOR'ed with
   // the record's sequence number, however, Web Push encryption is limited to a
   // single record per draft-ietf-webpush-encryption.
 
   return hkdf.client_write_key().as_string();
 }
 
 }  // namespace gcm