CSS: Avoid invalidating style when only descendants need updating

Source/core/css/invalidation/InvalidationSet.h

Index: Source/core/css/invalidation/InvalidationSet.h
diff --git a/Source/core/css/invalidation/InvalidationSet.h b/Source/core/css/invalidation/InvalidationSet.h
index fcc8fbc592924058354873997ec069a6a8f84dc8..28bc2ce50ffeb8fcf0eab90ed253b34854c900d3 100644
--- a/Source/core/css/invalidation/InvalidationSet.h
+++ b/Source/core/css/invalidation/InvalidationSet.h
@@ -69,6 +69,9 @@ public:
     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; }
 
@@ -105,6 +108,9 @@ private:
     // 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;