Fix HashTable growth strategy to be 2x instead of 4x

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 3105 matching lines @@
 
 
 void HashTableBase::ElementsRemoved(int n) {
   SetNumberOfElements(NumberOfElements() - n);
   SetNumberOfDeletedElements(NumberOfDeletedElements() + n);
 }
 
 
 // static
 int HashTableBase::ComputeCapacity(int at_least_space_for) {
-  int capacity = base::bits::RoundUpToPowerOfTwo32(at_least_space_for * 2);
+  // Add 50% slack to make slot collisions sufficiently unlikely.
+  // See matching computation in HashTable::HasSufficientCapacityToAdd().
+  // Must be kept in sync with CodeStubAssembler::HashTableComputeCapacity().
+  int raw_cap = at_least_space_for + (at_least_space_for >> 1);
+  int capacity = base::bits::RoundUpToPowerOfTwo32(raw_cap);
   return Max(capacity, kMinCapacity);
 }
 
 bool HashTableBase::IsKey(Isolate* isolate, Object* k) {
   Heap* heap = isolate->heap();
   return k != heap->the_hole_value() && k != heap->undefined_value();
 }
 
 void HashTableBase::SetNumberOfElements(int nof) {
   set(kNumberOfElementsIndex, Smi::FromInt(nof));
@@ skipping 5237 matching lines @@
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_INL_H_