Convert //chrome/browser/extensions from scoped_ptr to std::unique_ptr

chrome/browser/extensions/api/system_private/system_private_api.cc

Index: chrome/browser/extensions/api/system_private/system_private_api.cc
diff --git a/chrome/browser/extensions/api/system_private/system_private_api.cc b/chrome/browser/extensions/api/system_private/system_private_api.cc
index 4f3343d3e281a5d8377a5f77424155bf270d8bef..6f3f94c1a26aff8c7c1a427e05ce319f08ecf5e3 100644
--- a/chrome/browser/extensions/api/system_private/system_private_api.cc
+++ b/chrome/browser/extensions/api/system_private/system_private_api.cc
@@ -54,7 +54,7 @@ const char kUpdatingState[] = "Updating";
 void DispatchEvent(extensions::events::HistogramValue histogram_value,
                    const std::string& event_name,
                    base::Value* argument) {
-  scoped_ptr<base::ListValue> list_args(new base::ListValue());
+  std::unique_ptr<base::ListValue> list_args(new base::ListValue());
   if (argument) {
     list_args->Append(argument);
   }