Introducing GlobalDictionary, a backing store for global objects.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index f2c21ac4bd6dc157dec41203fa8de6aee7a1611b..2f55d71e725c3f63f0630e2a89c2381cef858f19 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -905,6 +905,9 @@ bool Object::IsNameDictionary() const {
 }
 
 
+bool Object::IsGlobalDictionary() const { return IsDictionary(); }
+
+
 bool Object::IsSeededNumberDictionary() const {
   return IsDictionary();
 }
@@ -3382,6 +3385,7 @@ CAST_ACCESSOR(FixedArrayBase)
 CAST_ACCESSOR(FixedDoubleArray)
 CAST_ACCESSOR(FixedTypedArrayBase)
 CAST_ACCESSOR(Foreign)
+CAST_ACCESSOR(GlobalDictionary)
 CAST_ACCESSOR(GlobalObject)
 CAST_ACCESSOR(HandlerTable)
 CAST_ACCESSOR(HeapObject)
@@ -6731,10 +6735,20 @@ bool JSObject::HasIndexedInterceptor() {
 
 NameDictionary* JSObject::property_dictionary() {
   DCHECK(!HasFastProperties());
+  // TODO(ishell): Uncomment, once all property_dictionary() usages for global
+  // objects are replaced with global_dictionary().
+  // DCHECK(!IsGlobalObject());
   return NameDictionary::cast(properties());
 }
 
 
+GlobalDictionary* JSObject::global_dictionary() {
+  DCHECK(!HasFastProperties());
+  DCHECK(IsGlobalObject());
+  return GlobalDictionary::cast(properties());
+}
+
+
 SeededNumberDictionary* JSObject::element_dictionary() {
   DCHECK(HasDictionaryElements());
   return SeededNumberDictionary::cast(elements());