Improve fast to slow elements conversion:

src/objects-inl.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 1949 matching lines @@
 
 void DescriptorArray::Swap(int first, int second) {
   fast_swap(this, ToKeyIndex(first), ToKeyIndex(second));
   FixedArray* content_array = GetContentArray();
   fast_swap(content_array, ToValueIndex(first), ToValueIndex(second));
   fast_swap(content_array, ToDetailsIndex(first),  ToDetailsIndex(second));
 }
 
 
 template<typename Shape, typename Key>
+int HashTable<Shape, Key>::ComputeCapacity(int at_least_space_for) {
+  const int kMinCapacity = 32;
+  int capacity = RoundUpToPowerOf2(at_least_space_for * 2);
+  if (capacity < kMinCapacity) {
+    capacity = kMinCapacity;  // Guarantee min capacity.
+  }
+  return capacity;
+}
+
+
+template<typename Shape, typename Key>
 int HashTable<Shape, Key>::FindEntry(Key key) {
   return FindEntry(GetIsolate(), key);
 }
 
 
 // Find entry for key otherwise return kNotFound.
 template<typename Shape, typename Key>
 int HashTable<Shape, Key>::FindEntry(Isolate* isolate, Key key) {
   uint32_t capacity = Capacity();
   uint32_t entry = FirstProbe(Shape::Hash(key), capacity);
@@ skipping 2520 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_