Optimize add/set/delete operations for string keys in Maps and Sets

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index bb9ecee0172d71b6348f4e90ed0ee3c7bc5e5850..bb8e9af15e900c3131b65640165e77e3f70df650 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -3915,10 +3915,14 @@ class OrderedHashTable: public FixedArray {
       kHeaderSize + kNumberOfBucketsIndex * kPointerSize;
   static const int kNumberOfElementsOffset =
       kHeaderSize + kNumberOfElementsIndex * kPointerSize;
+  static const int kNumberOfDeletedElementsOffset =
+      kHeaderSize + kNumberOfDeletedElementsIndex * kPointerSize;
 
   static const int kEntrySize = entrysize + 1;
   static const int kChainOffset = entrysize;
 
+  static const int kLoadFactor = 2;
+
  private:
   static Handle<Derived> Rehash(Handle<Derived> table, int new_capacity);
 
@@ -3963,7 +3967,6 @@ class OrderedHashTable: public FixedArray {
   static const int kNextTableIndex = kNumberOfElementsIndex;
   static const int kRemovedHolesIndex = kHashTableStartIndex;
 
-  static const int kLoadFactor = 2;
   static const int kMaxCapacity =
       (FixedArray::kMaxLength - kHashTableStartIndex)
       / (1 + (kEntrySize * kLoadFactor));