Move hash code from hidden string to a private symbol

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index e024c947650b96268c3fd71f6b25617f19073fbf..a979dc5a26aaea535241ff214da9681cf1fb024e 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -271,7 +271,6 @@ namespace internal {
   V(illegal_access_string, "illegal access")                   \
   V(cell_value_string, "%cell_value")                          \
   V(illegal_argument_string, "illegal argument")               \
-  V(identity_hash_string, "v8::IdentityHash")                  \
   V(closure_string, "(closure)")                               \
   V(dot_string, ".")                                           \
   V(compare_ic_string, "==")                                   \
@@ -294,6 +293,7 @@ namespace internal {
 #define PRIVATE_SYMBOL_LIST(V)      \
   V(nonextensible_symbol)           \
   V(sealed_symbol)                  \
+  V(hash_code_symbol)               \
   V(frozen_symbol)                  \
   V(nonexistent_symbol)             \
   V(elements_transition_symbol)     \
@@ -1741,6 +1741,8 @@ class Heap {
   // any string when looked up in properties.
   String* hidden_string_;
 
+  void AddPrivateGlobalSymbols(Handle<Object> private_intern_table);
+
   // GC callback function, called before and after mark-compact GC.
   // Allocations in the callback function are disallowed.
   struct GCPrologueCallbackPair {