Fix json_schema_compiler utils

tools/json_schema_compiler/util.cc

Index: tools/json_schema_compiler/util.cc
diff --git a/tools/json_schema_compiler/util.cc b/tools/json_schema_compiler/util.cc
index b0e98f64477c3fe840ec7ea682a1b1cc42c0b45e..468df83b297ab0407c3983e4cdf5eb109ef78fd2 100644
--- a/tools/json_schema_compiler/util.cc
+++ b/tools/json_schema_compiler/util.cc
@@ -47,7 +47,7 @@ void AddItemToList(const double from, base::ListValue* out) {
 void AddItemToList(const std::string& from, base::ListValue* out) {
   out->Append(base::Value::CreateStringValue(from));
 }
-void AddItemToList(const linked_ptr<base::DictionaryValue> from,
+void AddItemToList(const linked_ptr<base::DictionaryValue>& from,
     base::ListValue* out) {
   out->Append(static_cast<Value*>(from->DeepCopy()));
 }