Use std::unique_ptr for base::DictionaryValue and base::ListValue's internal store.

base/json/json_writer.cc

Index: base/json/json_writer.cc
diff --git a/base/json/json_writer.cc b/base/json/json_writer.cc
index 19bc0da972fc76eb9705682991ef571d8b09ee3e..0b658eed59d6bec7ea881acc4f385ba9c33b6c06 100644
--- a/base/json/json_writer.cc
+++ b/base/json/json_writer.cc
@@ -127,9 +127,7 @@ bool JSONWriter::BuildJSONString(const Value& node, size_t depth) {
       bool first_value_has_been_output = false;
       bool result = node.GetAsList(&list);
       DCHECK(result);
-      for (ListValue::const_iterator it = list->begin(); it != list->end();
-           ++it) {
-        const Value* value = *it;
+      for (const auto& value : *list) {
         if (omit_binary_values_ && value->GetType() == Value::TYPE_BINARY)
           continue;