android: Enable -Wunused-const-variable.

net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc

Index: net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc
diff --git a/net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc b/net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc
index cbc7a8426d334084590eb088a82dd38b33d2e7a7..56317fdd3c4e17572aa40c5ec581185b059e3272 100644
--- a/net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc
+++ b/net/quic/crypto/aes_128_gcm_12_decrypter_openssl.cc
@@ -12,14 +12,9 @@ using base::StringPiece;
 
 namespace net {
 
-namespace {
-
-const size_t kKeySize = 16;
 const size_t kNoncePrefixSize = 4;
 const size_t kAESNonceSize = 12;
 
-}  // namespace
-
 Aes128Gcm12Decrypter::Aes128Gcm12Decrypter() {}
 
 Aes128Gcm12Decrypter::~Aes128Gcm12Decrypter() {}