Object.observe: include oldValue in change records,

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 87ae24ab640f02d1e73e9291a81743a241ac5eec..1d15ad0007893a40f381de7c4a10ae80d325905e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1498,10 +1498,10 @@ class JSReceiver: public HeapObject {
   Smi* GenerateIdentityHash();
 
  private:
-  PropertyAttributes GetPropertyAttribute(JSReceiver* receiver,
-                                          LookupResult* result,
-                                          String* name,
-                                          bool continue_search);
+  PropertyAttributes GetPropertyAttributeForResult(JSReceiver* receiver,
+                                                   LookupResult* result,
+                                                   String* name,
+                                                   bool continue_search);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSReceiver);
 };