Remove base::Value::CreateNullValue

chrome/browser/policy/test/local_policy_test_server.cc

Index: chrome/browser/policy/test/local_policy_test_server.cc
diff --git a/chrome/browser/policy/test/local_policy_test_server.cc b/chrome/browser/policy/test/local_policy_test_server.cc
index a3bf21a29e38171b58531e7c9f9979809a1f72fe..0f9a9d9a46c2ce9dfd8775582f170c4b71b8ec7f 100644
--- a/chrome/browser/policy/test/local_policy_test_server.cc
+++ b/chrome/browser/policy/test/local_policy_test_server.cc
@@ -13,6 +13,7 @@
 #include "base/base_paths.h"
 #include "base/files/file_util.h"
 #include "base/json/json_writer.h"
+#include "base/memory/ptr_util.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/path_service.h"
 #include "base/strings/stringprintf.h"
@@ -245,7 +246,7 @@ bool LocalPolicyTestServer::GenerateAdditionalArguments(
     arguments->SetString("policy-key", policy_key_.AsUTF8Unsafe());
   if (automatic_rotation_of_signing_keys_enabled_) {
     arguments->Set("rotate-policy-keys-automatically",
-                   base::Value::CreateNullValue());
+                   base::MakeUnique<base::Value>());
   }
   if (server_data_dir_.IsValid()) {
     arguments->SetString("data-dir", server_data_dir_.GetPath().AsUTF8Unsafe());