In-place trimming of descriptor array when appending callbacks.

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 2617 matching lines @@
   bool IsConsistentWithBackPointers(Map* current_map);
 
   // Are two DescriptorArrays equal?
   bool IsEqualTo(DescriptorArray* other);
 #endif
 
   // The maximum number of descriptors we want in a descriptor array (should
   // fit in a page).
   static const int kMaxNumberOfDescriptors = 1024 + 512;
 
+  static int SizeFor(int number_of_descriptors) {
+    return ToKeyIndex(number_of_descriptors);
+  }
+
  private:
   // An entry in a DescriptorArray, represented as an (array, index) pair.
   class Entry {
    public:
     inline explicit Entry(DescriptorArray* descs, int index) :
         descs_(descs), index_(index) { }
 
     inline PropertyType type() { return descs_->GetType(index_); }
     inline Object* GetCallbackObject() { return descs_->GetValue(index_); }
 
@@ skipping 2306 matching lines @@
 
   // Clears the code cache.
   inline void ClearCodeCache(Heap* heap);
 
   // Update code cache.
   static void UpdateCodeCache(Handle<Map> map,
                               Handle<String> name,
                               Handle<Code> code);
   MUST_USE_RESULT MaybeObject* UpdateCodeCache(String* name, Code* code);
 
+  // Extend the descriptor array of the map with the list of descriptors.
+  // In case of duplicates, the latest descriptor is used.
+  static void CopyAppendCallbackDescriptors(Handle<Map> map,
+                                            Handle<Object> descriptors);
+
   // Returns the found code or undefined if absent.
   Object* FindInCodeCache(String* name, Code::Flags flags);
 
   // Returns the non-negative index of the code object if it is in the
   // cache and -1 otherwise.
   int IndexInCodeCache(Object* name, Code* code);
 
   // Removes a code object from the code cache at the given index.
   void RemoveFromCodeCache(String* name, Code* code, int index);
 
@@ skipping 3924 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_