Remove base::Value::CreateNullValue

chrome/browser/devtools/devtools_file_helper.cc

Index: chrome/browser/devtools/devtools_file_helper.cc
diff --git a/chrome/browser/devtools/devtools_file_helper.cc b/chrome/browser/devtools/devtools_file_helper.cc
index b5ef95fcc5a0424caec005cd75200de0c64f6138..a62a3dd0e91ba6704a27560e579cbd29ee543355 100644
--- a/chrome/browser/devtools/devtools_file_helper.cc
+++ b/chrome/browser/devtools/devtools_file_helper.cc
@@ -13,6 +13,7 @@
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/md5.h"
+#include "base/memory/ptr_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/value_conversions.h"
 #include "chrome/browser/browser_process.h"
@@ -385,7 +386,7 @@ void DevToolsFileHelper::AddUserConfirmedFileSystem(
                               prefs::kDevToolsFileSystemPaths);
   base::DictionaryValue* file_systems_paths_value = update.Get();
   file_systems_paths_value->SetWithoutPathExpansion(
-      file_system_path, base::Value::CreateNullValue());
+      file_system_path, base::MakeUnique<base::Value>());
 }
 
 std::vector<DevToolsFileHelper::FileSystem>