Support tag names as invalidation set features.

Source/core/css/invalidation/DescendantInvalidationSet.h

 /*
  * Copyright (C) 2014 Google 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:
  *
  *     * 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
@@ skipping 49 matching lines @@
 
     // Appends the classes in this DescendantInvalidationSet to the vector.
     void getClasses(Vector<AtomicString>& classes) const;
 
     // Appends the attributes in this DescendantInvalidationSet to the vector.
     void getAttributes(Vector<AtomicString>& attributes) const;
 
     // Appends the ids in this DescendantInvalidationSet to the vector.
     void getIds(Vector<AtomicString>& ids) const;
 
+    // Appends the tag names in this DescendantInvalidationSet to the vector.
+    void getTagNames(Vector<AtomicString>& tagNames) const;
+
     void setWholeSubtreeInvalid();
     bool wholeSubtreeInvalid() const { return m_allDescendantsMightBeInvalid; }
 
     void setCustomPseudoInvalid() { m_customPseudoInvalid = true; }
     bool customPseudoInvalid() const { return m_customPseudoInvalid; }
 
 private:
     DescendantInvalidationSet();
 
     HashSet<AtomicString>& ensureClassSet();
@@ skipping 10 matching lines @@
     // FIXME: optimize this if it becomes a memory issue.
     OwnPtr<HashSet<AtomicString> > m_classes;
     OwnPtr<HashSet<AtomicString> > m_ids;
     OwnPtr<HashSet<AtomicString> > m_tagNames;
     OwnPtr<HashSet<AtomicString> > m_attributes;
 };
 
 } // namespace WebCore
 
 #endif // DescendantInvalidationSet_h