Recalc sibling styles for forward positional rules on mutations only.

Source/core/dom/ElementRareData.h

Index: Source/core/dom/ElementRareData.h
diff --git a/Source/core/dom/ElementRareData.h b/Source/core/dom/ElementRareData.h
index 40942a5743ee012179e069e56b5d8865e4556403..84d04befacb871bfbdaa1cf087515548b8c71bfc 100644
--- a/Source/core/dom/ElementRareData.h
+++ b/Source/core/dom/ElementRareData.h
@@ -84,6 +84,8 @@ public:
     void setChildrenAffectedByLastChildRules(bool value) { m_childrenAffectedByLastChildRules = value; }
     bool childrenAffectedByDirectAdjacentRules() const { return m_childrenAffectedByDirectAdjacentRules; }
     void setChildrenAffectedByDirectAdjacentRules(bool value) { m_childrenAffectedByDirectAdjacentRules = value; }
+    bool childrenAffectedByIndirectAdjacentRules() const { return m_childrenAffectedByIndirectAdjacentRules; }
+    void setChildrenAffectedByIndirectAdjacentRules(bool value) { m_childrenAffectedByIndirectAdjacentRules = value; }
     bool childrenAffectedByForwardPositionalRules() const { return m_childrenAffectedByForwardPositionalRules; }
     void setChildrenAffectedByForwardPositionalRules(bool value) { m_childrenAffectedByForwardPositionalRules = value; }
     bool childrenAffectedByBackwardPositionalRules() const { return m_childrenAffectedByBackwardPositionalRules; }
@@ -167,6 +169,7 @@ private:
     unsigned m_childrenAffectedByFirstChildRules : 1;
     unsigned m_childrenAffectedByLastChildRules : 1;
     unsigned m_childrenAffectedByDirectAdjacentRules : 1;
+    unsigned m_childrenAffectedByIndirectAdjacentRules : 1;
     unsigned m_childrenAffectedByForwardPositionalRules : 1;
     unsigned m_childrenAffectedByBackwardPositionalRules : 1;
 
@@ -212,6 +215,7 @@ inline ElementRareData::ElementRareData(RenderObject* renderer)
     , m_childrenAffectedByFirstChildRules(false)
     , m_childrenAffectedByLastChildRules(false)
     , m_childrenAffectedByDirectAdjacentRules(false)
+    , m_childrenAffectedByIndirectAdjacentRules(false)
     , m_childrenAffectedByForwardPositionalRules(false)
     , m_childrenAffectedByBackwardPositionalRules(false)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
@@ -290,6 +294,7 @@ inline void ElementRareData::resetDynamicRestyleObservations()
     setChildrenAffectedByFirstChildRules(false);
     setChildrenAffectedByLastChildRules(false);
     setChildrenAffectedByDirectAdjacentRules(false);
+    setChildrenAffectedByIndirectAdjacentRules(false);
     setChildrenAffectedByForwardPositionalRules(false);
     setChildrenAffectedByBackwardPositionalRules(false);
 }