Sibling invalidation sets

Source/core/css/invalidation/DescendantInvalidationSet.cpp

Index: Source/core/css/invalidation/DescendantInvalidationSet.cpp
diff --git a/Source/core/css/invalidation/DescendantInvalidationSet.cpp b/Source/core/css/invalidation/DescendantInvalidationSet.cpp
index 6b4a355730a5dd2e354e25ec86e423c602ad7d7d..dcea057a329fa9406215f678ae481033b39f4389 100644
--- a/Source/core/css/invalidation/DescendantInvalidationSet.cpp
+++ b/Source/core/css/invalidation/DescendantInvalidationSet.cpp
@@ -52,7 +52,8 @@ void DescendantInvalidationSet::cacheTracingFlag()
 }
 
 DescendantInvalidationSet::DescendantInvalidationSet()
-    : m_allDescendantsMightBeInvalid(false)
+    : m_maxDirectAdjacentSelectors(1)
+    , m_allDescendantsMightBeInvalid(false)
     , m_customPseudoInvalid(false)
     , m_treeBoundaryCrossing(false)
     , m_insertionPointCrossing(false)
@@ -98,6 +99,8 @@ bool DescendantInvalidationSet::invalidatesElement(Element& element) const
 
 void DescendantInvalidationSet::combine(const DescendantInvalidationSet& other)
 {
+    m_maxDirectAdjacentSelectors = std::max(m_maxDirectAdjacentSelectors, other.m_maxDirectAdjacentSelectors);
+
     // No longer bother combining data structures, since the whole subtree is deemed invalid.
     if (wholeSubtreeInvalid())
         return;