Add removeAll method to sets and maps and use them

Source/wtf/HashSet.h

Index: Source/wtf/HashSet.h
diff --git a/Source/wtf/HashSet.h b/Source/wtf/HashSet.h
index 090f1cf589c60a5cfb82ec99c8b7ad30e8589f28..02c099f947f128faf32e2ccc739ce199213eafd7 100644
--- a/Source/wtf/HashSet.h
+++ b/Source/wtf/HashSet.h
@@ -99,6 +99,8 @@ namespace WTF {
         void remove(ValuePeekInType);
         void remove(iterator);
         void clear();
+        template<typename Collection>
+        void removeAll(const Collection& other);
 
         static bool isValidValue(ValuePeekInType);
 
@@ -218,6 +220,18 @@ namespace WTF {
     }
 
     template<typename T, typename U, typename V, typename W>
+    template<typename Collection>
+    inline void HashSet<T, U, V, W>::removeAll(const Collection& other)
+    {
+        if (other.isEmpty() || isEmpty())
+            return;
+        typedef typename Collection::const_iterator CollectionIterator;
+        CollectionIterator otherEnd(other.end());
+        for (CollectionIterator it(other.begin()); it != otherEnd; ++it)
+            remove(*it);
+    }
+
+    template<typename T, typename U, typename V, typename W>
     inline bool HashSet<T, U, V, W>::isValidValue(ValuePeekInType value)
     {
         if (ValueTraits::isDeletedValue(value))