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

src/objects.h

 // 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 126 matching lines @@
   inline Smi* AsSmi();
 
   PropertyType type() { return TypeField::decode(value_); }
 
   bool IsTransition() {
     PropertyType t = type();
     ASSERT(t != INTERCEPTOR);
     return t == MAP_TRANSITION || t == CONSTANT_TRANSITION;
   }
 
+  bool IsProperty() {
+    return type() < FIRST_PHANTOM_PROPERTY_TYPE;
+  }
+
   PropertyAttributes attributes() { return AttributesField::decode(value_); }
 
   int index() { return IndexField::decode(value_); }
 
   static bool IsValidIndex(int index) { return IndexField::is_valid(index); }
 
   bool IsReadOnly() { return (attributes() & READ_ONLY) != 0; }
   bool IsDontDelete() { return (attributes() & DONT_DELETE) != 0; }
   bool IsDontEnum() { return (attributes() & DONT_ENUM) != 0; }
 
@@ skipping 1554 matching lines @@
   static int ToKeyIndex(int descriptor_number) {
     return descriptor_number+kFirstIndex;
   }
   static int ToValueIndex(int descriptor_number) {
     return descriptor_number << 1;
   }
   static int ToDetailsIndex(int descriptor_number) {
     return( descriptor_number << 1) + 1;
   }
 
+  bool is_null_descriptor(int descriptor_number) {
+    return PropertyDetails(GetDetails(descriptor_number)).type() ==
+        NULL_DESCRIPTOR;
+  }
   // Swap operation on FixedArray without using write barriers.
   static inline void fast_swap(FixedArray* array, int first, int second);
 
   // Swap descriptor first and second.
   inline void Swap(int first, int second);
 
   FixedArray* GetContentArray() {
     return FixedArray::cast(get(kContentArrayIndex));
   }
   DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
@@ skipping 2525 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_