Recalc sibling styles for forward positional rules on mutations only.

Source/core/dom/shadow/ShadowRoot.cpp

Index: Source/core/dom/shadow/ShadowRoot.cpp
diff --git a/Source/core/dom/shadow/ShadowRoot.cpp b/Source/core/dom/shadow/ShadowRoot.cpp
index c781db09eb017b6ff29737f52bc90e334661e05c..630b10dcb1954cdbb2fea42e080db395ed4248c0 100644
--- a/Source/core/dom/shadow/ShadowRoot.cpp
+++ b/Source/core/dom/shadow/ShadowRoot.cpp
@@ -411,6 +411,7 @@ bool ShadowRoot::childrenSupportStyleSharing() const
     return !m_shadowRootRareData->childrenAffectedByFirstChildRules()
         && !m_shadowRootRareData->childrenAffectedByLastChildRules()
         && !m_shadowRootRareData->childrenAffectedByDirectAdjacentRules()
+        && !m_shadowRootRareData->childrenAffectedByIndirectAdjacentRules()
         && !m_shadowRootRareData->childrenAffectedByForwardPositionalRules()
         && !m_shadowRootRareData->childrenAffectedByBackwardPositionalRules();
 }
@@ -435,6 +436,11 @@ bool ShadowRoot::childrenAffectedByDirectAdjacentRules() const
     return m_shadowRootRareData && m_shadowRootRareData->childrenAffectedByDirectAdjacentRules();
 }
 
+bool ShadowRoot::childrenAffectedByIndirectAdjacentRules() const
+{
+    return m_shadowRootRareData && m_shadowRootRareData->childrenAffectedByIndirectAdjacentRules();
+}
+
 bool ShadowRoot::childrenAffectedByForwardPositionalRules() const
 {
     return m_shadowRootRareData && m_shadowRootRareData->childrenAffectedByForwardPositionalRules();
@@ -455,6 +461,11 @@ void ShadowRoot::setChildrenAffectedByDirectAdjacentRules()
     ensureShadowRootRareData()->setChildrenAffectedByDirectAdjacentRules(true);
 }
 
+void ShadowRoot::setChildrenAffectedByIndirectAdjacentRules()
+{
+    ensureShadowRootRareData()->setChildrenAffectedByIndirectAdjacentRules(true);
+}
+
 void ShadowRoot::setChildrenAffectedByBackwardPositionalRules()
 {
     ensureShadowRootRareData()->setChildrenAffectedByBackwardPositionalRules(true);