Re-land CL 9466047.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2571 matching lines @@
 
   // Are two DescriptorArrays equal?
   bool IsEqualTo(DescriptorArray* other);
 #endif
 
   // The maximum number of descriptors we want in a descriptor array (should
   // fit in a page).
   static const int kMaxNumberOfDescriptors = 1024 + 512;
 
  private:
+  // An entry in a DescriptorArray, represented as an (array, index) pair.
+  class Entry {
+   public:
+    inline explicit Entry(DescriptorArray* descs, int index) :
+        descs_(descs), index_(index) { }
+
+    inline PropertyType type() { return descs_->GetType(index_); }
+    inline Object* GetCallbackObject() { return descs_->GetValue(index_); }
+
+   private:
+    DescriptorArray* descs_;
+    int index_;
+  };
+
   // Conversion from descriptor number to array indices.
   static int ToKeyIndex(int descriptor_number) {
     return descriptor_number+kFirstIndex;
   }
 
   static int ToDetailsIndex(int descriptor_number) {
     return (descriptor_number << 1) + 1;
   }
 
   static int ToValueIndex(int descriptor_number) {
@@ skipping 5313 matching lines @@
 
   // TODO(svenpanne) Evil temporary helper, will vanish soon...
   void set(bool modify_getter, Object* value) {
     if (modify_getter) {
       set_getter(value);
     } else {
       set_setter(value);
     }
   }
 
+  bool ContainsAccessor() {
+    return IsJSAccessor(getter()) || IsJSAccessor(setter());
+  }
+
 #ifdef OBJECT_PRINT
   void AccessorPairPrint(FILE* out = stdout);
 #endif
 #ifdef DEBUG
   void AccessorPairVerify();
 #endif
 
   static const int kGetterOffset = HeapObject::kHeaderSize;
   static const int kSetterOffset = kGetterOffset + kPointerSize;
   static const int kSize = kSetterOffset + kPointerSize;
 
  private:
+  // Strangely enough, in addition to functions and harmony proxies, the spec
+  // requires us to consider undefined as a kind of accessor, too:
+  //    var obj = {};
+  //    Object.defineProperty(obj, "foo", {get: undefined});
+  //    assertTrue("foo" in obj);
+  bool IsJSAccessor(Object* obj) {
+    return obj->IsSpecFunction() || obj->IsUndefined();
+  }
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(AccessorPair);
 };
 
 
 class AccessCheckInfo: public Struct {
  public:
   DECL_ACCESSORS(named_callback, Object)
   DECL_ACCESSORS(indexed_callback, Object)
   DECL_ACCESSORS(data, Object)
 
@@ skipping 479 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_