Object.observe: Handle oldValue for elements with accessors properly.

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 1817 matching lines @@
   // represented in a FixedDoubleArray and has at least one value that can only
   // be represented as a double and not a Smi.
   bool ShouldConvertToFastDoubleElements(bool* has_smi_only_elements);
 
   // Computes the new capacity when expanding the elements of a JSObject.
   static int NewElementsCapacity(int old_capacity) {
     // (old_capacity + 50%) + 16
     return old_capacity + (old_capacity >> 1) + 16;
   }
 
+  PropertyType GetLocalPropertyType(String* name);
+  PropertyType GetLocalElementType(uint32_t index);
+  AccessorPair* GetLocalPropertyAccessorPair(String* name);
+  AccessorPair* GetLocalElementAccessorPair(uint32_t index);
+
   // Tells whether the index'th element is present and how it is stored.
-  enum LocalElementType {
+  enum LocalElementKind {
     // There is no element with given index.
     UNDEFINED_ELEMENT,
 
     // Element with given index is handled by interceptor.
     INTERCEPTED_ELEMENT,
 
     // Element with given index is character in string.
     STRING_CHARACTER_ELEMENT,
 
     // Element with given index is stored in fast backing store.
     FAST_ELEMENT,
 
     // Element with given index is stored in slow backing store.
     DICTIONARY_ELEMENT
   };
 
-  LocalElementType GetLocalElementType(uint32_t index);
+  LocalElementKind GetLocalElementKind(uint32_t index);
 
   MUST_USE_RESULT MaybeObject* SetFastElement(uint32_t index,
                                               Object* value,
                                               StrictModeFlag strict_mode,
                                               bool check_prototype);
 
   MUST_USE_RESULT MaybeObject* SetDictionaryElement(
       uint32_t index,
       Object* value,
       PropertyAttributes attributes,
@@ skipping 7169 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_