Put V8 extras into the snapshot

src/snapshot/serialize.h

Index: src/snapshot/serialize.h
diff --git a/src/snapshot/serialize.h b/src/snapshot/serialize.h
index c92683dfccc035e566c46f36cc6d52e01ae49117..780ce0f83428b13023f84690a16ce4faa8b3ae4c 100644
--- a/src/snapshot/serialize.h
+++ b/src/snapshot/serialize.h
@@ -401,8 +401,11 @@ class SerializerDeserializer: public ObjectVisitor {
   // Used for the source code for compiled stubs, which is in the executable,
   // but is referred to from external strings in the snapshot.
   static const int kCodeStubNativesStringResource = 0x5d;
+  // Used for the source code for V8 extras, which is in the executable,
+  // but is referred to from external strings in the snapshot.
+  static const int kExtraNativesStringResource = 0x5e;

[domenic, 2015/08/12 19:44:12]

Wasn't sure if there was a pattern here that was supposed to be followed so I
just took an unused code...

 
-  // 0x5e..0x5f unused
+  // 0x5f unused
 
   // ---------- byte code range 0x80..0xff ----------
   // First 32 root array items.