[modules] Give Module an internal [hash] field

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 34b0f91f05f27e8ec22b5ca9419de0b9611521dc..7c29880abcd96c315a3eb31dc362c2ad4f8860ac 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1069,6 +1069,10 @@ class Isolate {
 
   base::RandomNumberGenerator* random_number_generator();
 
+  // Generates a random number that is non-zero when masked
+  // with the provided mask.
+  int GenerateIdentityHash(uint32_t mask);
+
   // Given an address occupied by a live code object, return that object.
   Object* FindCodeObject(Address a);