Shrink dictionaries on deletion if number of elements are less than a

src/objects.h

 // Copyright 2011 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 2572 matching lines @@
   }
 
   static uint32_t FirstProbe(uint32_t hash, uint32_t size) {
     return hash & (size - 1);
   }
 
   static uint32_t NextProbe(uint32_t last, uint32_t number, uint32_t size) {
     return (last + number) & (size - 1);
   }
 
+  // Rehashes this hash-table into the new table.
+  MUST_USE_RESULT MaybeObject* Rehash(HashTable* new_table, Key key);
+
+  // Attempt to shrink hash table after removal of key.
+  MUST_USE_RESULT MaybeObject* Shrink(Key key);
+
   // Ensure enough space for n additional elements.
   MUST_USE_RESULT MaybeObject* EnsureCapacity(int n, Key key);
 };
 
 
 
 // HashTableKey is an abstract superclass for virtual key behavior.
 class HashTableKey {
  public:
   // Returns whether the other object matches this key.
@@ skipping 144 matching lines @@
   void DetailsAtPut(int entry, PropertyDetails value) {
     this->set(HashTable<Shape, Key>::EntryToIndex(entry) + 2, value.AsSmi());
   }
 
   // Sorting support
   void CopyValuesTo(FixedArray* elements);
 
   // Delete a property from the dictionary.
   Object* DeleteProperty(int entry, JSObject::DeleteMode mode);
 
+  // Attempt to shrink the dictionary after deletion of key.
+  MUST_USE_RESULT MaybeObject* Shrink(Key key);
+
   // Returns the number of elements in the dictionary filtering out properties
   // with the specified attributes.
   int NumberOfElementsFilterAttributes(PropertyAttributes filter);
 
   // Returns the number of enumerable elements in the dictionary.
   int NumberOfEnumElements();
 
   // Copies keys to preallocated fixed array.
   void CopyKeysTo(FixedArray* storage, PropertyAttributes filter);
   // Fill in details for properties into storage.
@@ skipping 4354 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_