Reapply revisions 1432, 1433, 1469 and 1472 while fixing issue 279.

src/objects-inl.h

Index: src/objects-inl.h
===================================================================
--- src/objects-inl.h	(revision 1544)
+++ src/objects-inl.h	(working copy)
@@ -1094,6 +1094,15 @@
 }
 
 
+Object* JSObject::InObjectPropertyAt(int index) {
+  // Adjust for the number of properties stored in the object.
+  index -= map()->inobject_properties();
+  ASSERT(index < 0);
+  int offset = map()->instance_size() + (index * kPointerSize);
+  return READ_FIELD(this, offset);
+}
+
+
 Object* JSObject::InObjectPropertyAtPut(int index,
                                         Object* value,
                                         WriteBarrierMode mode) {