chromeos: Add out-of-line copy ctors for complex classes.

chromeos/network/client_cert_util.cc

Index: chromeos/network/client_cert_util.cc
diff --git a/chromeos/network/client_cert_util.cc b/chromeos/network/client_cert_util.cc
index 0fface7e03cce2970b2f8dd038a74c62b77781a3..361664f27fa63ecf9a0a5a125b8100c8636bdd75 100644
--- a/chromeos/network/client_cert_util.cc
+++ b/chromeos/network/client_cert_util.cc
@@ -264,6 +264,8 @@ ClientCertConfig::ClientCertConfig()
       client_cert_type(onc::client_cert::kClientCertTypeNone) {
 }
 
+ClientCertConfig::ClientCertConfig(const ClientCertConfig& other) = default;
+
 void OncToClientCertConfig(const base::DictionaryValue& network_config,
                            ClientCertConfig* cert_config) {
   using namespace ::onc;