Fix for LinkedHashSet::swap.

Source/wtf/ListHashSetTest.cpp

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 638 matching lines @@
         ownPtr2 = set.take(ptr2);
         EXPECT_TRUE(set.isEmpty());
     }
     EXPECT_FALSE(deleted1);
     EXPECT_FALSE(deleted2);
 
     EXPECT_EQ(ptr1, ownPtr1);
     EXPECT_EQ(ptr2, ownPtr2);
 }
 
+template<typename Set>
+void swapTestHelper()
+{
+    int num = 10;
+    Set set0;
+    Set set1;
+    Set set2;
+    for (int i = 0; i < num; ++i) {
+        set1.add(i + 1);
+        set2.add(num - i);
+    }
+
+    typename Set::iterator it1 = set1.begin();
+    typename Set::iterator it2 = set2.begin();
+    for (int i = 0; i < num; ++i, ++it1, ++it2) {
+        EXPECT_EQ(*it1, i + 1);
+        EXPECT_EQ(*it2, num - i);
+    }
+    EXPECT_EQ(set0.begin(), set0.end());
+    EXPECT_EQ(it1, set1.end());
+    EXPECT_EQ(it2, set2.end());
+
+    // Shift sets: 2->1, 1->0, 0->2
+    set1.swap(set2); // Swap with non-empty sets.
+    set0.swap(set2); // Swap with an empty set.
+
+    it1 = set0.begin();
+    it2 = set1.begin();
+    for (int i = 0; i < num; ++i, ++it1, ++it2) {
+        EXPECT_EQ(*it1, i + 1);
+        EXPECT_EQ(*it2, num - i);
+    }
+    EXPECT_EQ(it1, set0.end());
+    EXPECT_EQ(it2, set1.end());
+    EXPECT_EQ(set2.begin(), set2.end());
+
+    int removedIndex = num >> 1;
+    set0.remove(removedIndex + 1);
+    set1.remove(num - removedIndex);
+
+    it1 = set0.begin();
+    it2 = set1.begin();
+    for (int i = 0; i < num; ++i, ++it1, ++it2) {
+        if (i == removedIndex)
+            ++i;
+        EXPECT_EQ(*it1, i + 1);
+        EXPECT_EQ(*it2, num - i);
+    }
+    EXPECT_EQ(it1, set0.end());
+    EXPECT_EQ(it2, set1.end());
+}
+
+TEST(ListHashSetTest, Swap)
+{
+    swapTestHelper<ListHashSet<int> >();
+}
+
+TEST(LinkedHashSetTest, Swap)
+{
+    swapTestHelper<LinkedHashSet<int> >();
+}
+
 } // namespace