[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 9fdff5054902fd22853065f5db31a61d1c0dfef2..860f703e13b126aa6e3b54517cc3e676d2e7051a 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);