Store client cert hashes as strings instead of StringPieces.

net/quic/crypto/quic_crypto_server_config.cc

Index: net/quic/crypto/quic_crypto_server_config.cc
diff --git a/net/quic/crypto/quic_crypto_server_config.cc b/net/quic/crypto/quic_crypto_server_config.cc
index 66453a7921be56e9ab479c8ab191c17ce63d1bae..2e804df96a620abd88027ab40e8937304c5a82a3 100644
--- a/net/quic/crypto/quic_crypto_server_config.cc
+++ b/net/quic/crypto/quic_crypto_server_config.cc
@@ -1138,8 +1138,13 @@ void QuicCryptoServerConfig::BuildRejection(
     return;
   }
 
-  client_hello.GetStringPiece(kCCS, &(params->client_common_set_hashes));
-  client_hello.GetStringPiece(kCCRT, &(params->client_cached_cert_hashes));
+  StringPiece client_common_set_hashes;
+  client_hello.GetStringPiece(kCCS, &client_common_set_hashes);
+  params->client_common_set_hashes = client_common_set_hashes.as_string();
+
+  StringPiece client_cached_cert_hashes;
+  client_hello.GetStringPiece(kCCRT, &client_cached_cert_hashes);
+  params->client_cached_cert_hashes = client_cached_cert_hashes.as_string();
 
   const string compressed = CertCompressor::CompressChain(
       *certs, params->client_common_set_hashes,