Fix CliCredentials reference

test/cpp/util/grpc_tool.cc

@@ -75,7 +75,7 @@ class GrpcTool {
             GrpcToolOutputCallback callback);
   bool CallMethod(int argc, const char** argv, const CliCredentials& cred,
                   GrpcToolOutputCallback callback);
-  bool PrintType(int argc, const char** argv, CliCredentials cred,
+  bool PrintType(int argc, const char** argv, const CliCredentials& cred,
                  GrpcToolOutputCallback callback);
   // TODO(zyc): implement the following methods
   // bool ListServices(int argc, const char** argv, GrpcToolOutputCallback
@@ -257,7 +257,8 @@ bool GrpcTool::Help(int argc, const char** argv, const CliCredentials& cred,
   return true;
 }
 
-bool GrpcTool::PrintType(int argc, const char** argv, CliCredentials cred,
+bool GrpcTool::PrintType(int argc, const char** argv,
+                         const CliCredentials& cred,
                          GrpcToolOutputCallback callback) {
   CommandUsage(
       "Print type\n"

test/cpp/util/grpc_tool_test.cc

@@ -109,7 +109,7 @@ class GrpcToolTest : public ::testing::Test {
 
   void ShutdownServer() { server_->Shutdown(); }
 
-  void ExitWhenError(int argc, const char** argv, const CliCredentials cred,
+  void ExitWhenError(int argc, const char** argv, const CliCredentials& cred,
                      GrpcToolOutputCallback callback) {
     int result = GrpcToolMainLib(argc, argv, cred, callback);
     if (result) {