Convert JsonWriter::Write to taking a const ref for the in-param

chromeos/network/network_configuration_handler_unittest.cc

Index: chromeos/network/network_configuration_handler_unittest.cc
diff --git a/chromeos/network/network_configuration_handler_unittest.cc b/chromeos/network/network_configuration_handler_unittest.cc
index 2772fc9b6d19d1faaa91c521f79459b754be00f9..2b79c4cb483b53209d18a9bb03302eb3b2a20c0d 100644
--- a/chromeos/network/network_configuration_handler_unittest.cc
+++ b/chromeos/network/network_configuration_handler_unittest.cc
@@ -46,7 +46,7 @@ namespace {
 static std::string PrettyJson(const base::DictionaryValue& value) {
   std::string pretty;
   base::JSONWriter::WriteWithOptions(
-      &value, base::JSONWriter::OPTIONS_PRETTY_PRINT, &pretty);
+      value, base::JSONWriter::OPTIONS_PRETTY_PRINT, &pretty);
   return pretty;
 }