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

components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc
index 786c7e5f06f81cefcf938de7024bd5f34300ba97..44ab9c1a99ebd11185d9bc688966d8a58b4b0168 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.cc
@@ -54,9 +54,8 @@ const StringToConstant kDataReductionProxyBypassActionTypeTable[] = {
 
 std::string JoinListValueStrings(base::ListValue* list_value) {
   std::vector<std::string> values;
-  for (auto it = list_value->begin(); it != list_value->end(); ++it) {
+  for (const auto& value : *list_value) {
     std::string value_string;
-    base::Value* value = *it;
     if (!value->GetAsString(&value_string))
       return std::string();