Introduce experimental natives that are enabled by a runtime flag.

src/natives.h

Index: src/natives.h
diff --git a/src/natives.h b/src/natives.h
index 1df94b08796041471a100f5452e3846a512ddec0..92f0d90b5df3c3e6b23e4fe03b08cfcc873c2c45 100644
--- a/src/natives.h
+++ b/src/natives.h
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -36,7 +36,7 @@ typedef bool (*NativeSourceCallback)(Vector<const char> name,
                                      int index);
 
 enum NativeType {
-  CORE, D8, I18N
+  CORE, EXPERIMENTAL, D8, I18N
 };
 
 template <NativeType type>
@@ -57,6 +57,7 @@ class NativesCollection {
 };
 
 typedef NativesCollection<CORE> Natives;
+typedef NativesCollection<EXPERIMENTAL> ExperimentalNatives;
 
 } }  // namespace v8::internal