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

ios/chrome/browser/ui/webui/history/browsing_history_handler.cc

Index: ios/chrome/browser/ui/webui/history/browsing_history_handler.cc
diff --git a/ios/chrome/browser/ui/webui/history/browsing_history_handler.cc b/ios/chrome/browser/ui/webui/history/browsing_history_handler.cc
index ea34137a673e82416bd575cb9a795800956af08f..b74497617c46c6396a544e77410af4e98c760c6d 100644
--- a/ios/chrome/browser/ui/webui/history/browsing_history_handler.cc
+++ b/ios/chrome/browser/ui/webui/history/browsing_history_handler.cc
@@ -456,7 +456,7 @@ void BrowsingHistoryHandler::HandleRemoveVisits(const base::ListValue* args) {
   expire_list.reserve(args->GetSize());
 
   DCHECK(urls_to_be_deleted_.empty());
-  for (base::Value* arg : *args) {
+  for (const auto& arg : *args) {
     base::DictionaryValue* deletion = NULL;
     base::string16 url;
     base::ListValue* timestamps = NULL;
@@ -478,7 +478,7 @@ void BrowsingHistoryHandler::HandleRemoveVisits(const base::ListValue* args) {
 
     double timestamp;
     history::ExpireHistoryArgs* expire_args = NULL;
-    for (base::Value* timestamp_value : *timestamps) {
+    for (const auto& timestamp_value : *timestamps) {
       if (!timestamp_value->GetAsDouble(&timestamp)) {
         NOTREACHED() << "Unable to extract visit timestamp.";
         continue;