Store JSGlobalProxy's identity hash directly on the proxy itself

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 34aff97aca81fe3c7d4c9afe7e15d39c823bcb2b..c4ada9116f6b31feabba79499b95fd77b96bc481 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1988,8 +1988,6 @@ class JSReceiver: public HeapObject {
       KeyCollectionType type);
 
  protected:
-  Smi* GenerateIdentityHash();
-
   MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithDefinedSetter(
       Handle<JSReceiver> object,
       Handle<JSReceiver> setter,
@@ -7709,6 +7707,9 @@ class JSGlobalProxy : public JSObject {
   // It is null value if this object is not used by any context.
   DECL_ACCESSORS(native_context, Object)
 
+  // [hash]: The hash code property (undefined if not initialized yet).
+  DECL_ACCESSORS(hash, Object)
+
   // Casting.
   static inline JSGlobalProxy* cast(Object* obj);
 
@@ -7720,7 +7721,8 @@ class JSGlobalProxy : public JSObject {
 
   // Layout description.
   static const int kNativeContextOffset = JSObject::kHeaderSize;
-  static const int kSize = kNativeContextOffset + kPointerSize;
+  static const int kHashOffset = kNativeContextOffset + kPointerSize;
+  static const int kSize = kHashOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSGlobalProxy);