Let DescriptorArray::Append insert at proper position, avoiding need for resorting.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 54dc0767b96bcadc06fb24c5dd7b4b95aaa75729..6b22140ff3497913f1bbefa2445d9e6911e7a2f9 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -496,9 +496,8 @@ class Factory {
       Handle<String> name,
       LanguageMode language_mode);
 
-  Handle<DescriptorArray> CopyAppendCallbackDescriptors(
-      Handle<DescriptorArray> array,
-      Handle<Object> descriptors);
+  void CopyAppendCallbackDescriptors(Handle<Map> map,
+                                     Handle<Object> descriptors);
 
   // Create a new map cache.
   Handle<MapCache> NewMapCache(int at_least_space_for);