CSS: Avoid invalidating style when only descendants need updating

Source/core/css/invalidation/InvalidationSet.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 51 matching lines @@
     void combine(const InvalidationSet& other);
 
     void addClass(const AtomicString& className);
     void addId(const AtomicString& id);
     void addTagName(const AtomicString& tagName);
     void addAttribute(const AtomicString& attributeLocalName);
 
     void setWholeSubtreeInvalid();
     bool wholeSubtreeInvalid() const { return m_allDescendantsMightBeInvalid; }
 
+    void setInvalidatesSelf() { m_invalidatesSelf = true; }
+    bool invalidatesSelf() const { return m_invalidatesSelf; }
+
     void setTreeBoundaryCrossing() { m_treeBoundaryCrossing = true; }
     bool treeBoundaryCrossing() const { return m_treeBoundaryCrossing; }
 
     void setInsertionPointCrossing() { m_insertionPointCrossing = true; }
     bool insertionPointCrossing() const { return m_insertionPointCrossing; }
 
     void setCustomPseudoInvalid() { m_customPseudoInvalid = true; }
     bool customPseudoInvalid() const { return m_customPseudoInvalid; }
 
     bool isEmpty() const { return !m_classes && !m_ids && !m_tagNames && !m_attributes && !m_customPseudoInvalid; }
@@ skipping 16 matching lines @@
 
     // FIXME: optimize this if it becomes a memory issue.
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_classes;
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_ids;
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_tagNames;
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_attributes;
 
     // If true, all descendants might be invalidated, so a full subtree recalc is required.
     unsigned m_allDescendantsMightBeInvalid : 1;
 
+    // If true, the element itself is invalid.
+    unsigned m_invalidatesSelf : 1;
+
     // If true, all descendants which are custom pseudo elements must be invalidated.
     unsigned m_customPseudoInvalid : 1;
 
     // If true, the invalidation must traverse into ShadowRoots with this set.
     unsigned m_treeBoundaryCrossing : 1;
 
     // If true, insertion point descendants must be invalidated.
     unsigned m_insertionPointCrossing : 1;
 };
 
 } // namespace blink
 
 #endif // InvalidationSet_h