move helper function into namespace

src/core/lib/security/credentials/google_default/google_default_credentials.cc

@@ -255,9 +255,6 @@ void set_gce_tenancy_checker_for_testing(grpc_gce_tenancy_checker checker) {
   g_gce_tenancy_checker = checker;
 }
 
-}  // namespace internal
-}  // namespace grpc_core
-
 void grpc_flush_cached_google_default_credentials(void) {
   grpc_core::ExecCtx exec_ctx;
   gpr_once_init(&g_once, init_default_credentials);
@@ -266,6 +263,9 @@ void grpc_flush_cached_google_default_credentials(void) {
   gpr_mu_unlock(&g_state_mu);
 }
 
+}  // namespace internal
+}  // namespace grpc_core
+
 /* -- Well known credentials path. -- */
 
 static grpc_well_known_credentials_path_getter creds_path_getter = nullptr;

src/core/lib/security/credentials/google_default/google_default_credentials.h

@@ -45,9 +45,6 @@ typedef struct {
   grpc_channel_credentials* ssl_creds;
 } grpc_google_default_channel_credentials;
 
-// TEST-ONLY. Reset the internal global state.
-void grpc_flush_cached_google_default_credentials(void);
-
 namespace grpc_core {
 namespace internal {
 
@@ -55,6 +52,9 @@ typedef bool (*grpc_gce_tenancy_checker)(void);
 
 void set_gce_tenancy_checker_for_testing(grpc_gce_tenancy_checker checker);
 
+// TEST-ONLY. Reset the internal global state.
+void grpc_flush_cached_google_default_credentials(void);
+
 }  // namespace internal
 }  // namespace grpc_core
 

test/core/security/credentials_test.cc

@@ -43,6 +43,7 @@
 #include "src/core/lib/security/transport/auth_filters.h"
 #include "test/core/util/test_config.h"
 
+using grpc_core::internal::grpc_flush_cached_google_default_credentials;
 using grpc_core::internal::set_gce_tenancy_checker_for_testing;
 
 /* -- Mock channel credentials. -- */