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

services/catalog/instance.cc

Index: services/catalog/instance.cc
diff --git a/services/catalog/instance.cc b/services/catalog/instance.cc
index 6673f35ab5eabd4928bde13bfad7cd187e1d2c2a..d90126646259f11c4fb207fd036f75430da0ba4a 100644
--- a/services/catalog/instance.cc
+++ b/services/catalog/instance.cc
@@ -145,9 +145,8 @@ void Instance::DeserializeCatalog() {
   CHECK(catalog);
   // TODO(sky): make this handle aliases.
   // TODO(beng): implement this properly!
-  for (auto it = catalog->begin(); it != catalog->end(); ++it) {
+  for (const auto& v : *catalog) {
     const base::DictionaryValue* dictionary = nullptr;
-    const base::Value* v = *it;
     CHECK(v->GetAsDictionary(&dictionary));
     std::unique_ptr<Entry> entry = Entry::Deserialize(*dictionary);
     // TODO(beng): user catalog.