Make V8 extras a separate type of native

src/snapshot/natives.h

Index: src/snapshot/natives.h
diff --git a/src/snapshot/natives.h b/src/snapshot/natives.h
index 8fda01c40479a712cc17b7deb9cae168a1d7914a..149f9ec2bed27de84b39e8093701138b941ad1e9 100644
--- a/src/snapshot/natives.h
+++ b/src/snapshot/natives.h
@@ -12,9 +12,7 @@ namespace v8 { class StartupData; }  // Forward declaration.
 namespace v8 {
 namespace internal {
 
-enum NativeType {
-  CORE, EXPERIMENTAL, D8, TEST
-};
+enum NativeType { CORE, EXPERIMENTAL, EXTRAS, D8, TEST };
 
 template <NativeType type>
 class NativesCollection {
@@ -36,6 +34,7 @@ class NativesCollection {
 
 typedef NativesCollection<CORE> Natives;
 typedef NativesCollection<EXPERIMENTAL> ExperimentalNatives;
+typedef NativesCollection<EXTRAS> ExtraNatives;
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 // Used for reading the natives at runtime. Implementation in natives-empty.cc