Fix garbage collection of unused maps. Null descriptors, created...

src/factory.cc

 // Copyright 2006-2008 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 518 matching lines @@
   int nof_callbacks = callbacks.length();
   Handle<DescriptorArray> result =
       NewDescriptorArray(array->number_of_descriptors() + nof_callbacks);
 
   // Number of descriptors added to the result so far.
   int descriptor_count = 0;
 
   // Copy the descriptors from the array.
   DescriptorWriter w(*result);
   for (DescriptorReader r(*array); !r.eos(); r.advance()) {
-    w.WriteFrom(&r);
+    if (!r.IsNullDescriptor()) {
+      w.WriteFrom(&r);
+    }
     descriptor_count++;
   }
 
   // Number of duplicates detected.
   int duplicates = 0;
 
   // Fill in new callback descriptors.  Process the callbacks from
   // back to front so that the last callback with a given name takes
   // precedence over previously added callbacks with that name.
   for (int i = nof_callbacks - 1; i >= 0; i--) {
@@ skipping 300 matching lines @@
     Execution::ConfigureInstance(instance,
                                  instance_template,
                                  pending_exception);
   } else {
     *pending_exception = false;
   }
 }
 
 
 } }  // namespace v8::internal