Support style invalidation for ::content.

Source/core/css/invalidation/StyleInvalidator.h

Index: Source/core/css/invalidation/StyleInvalidator.h
diff --git a/Source/core/css/invalidation/StyleInvalidator.h b/Source/core/css/invalidation/StyleInvalidator.h
index 829cc2b35bc28d48a96ebfc0355d44631b53c921..578ec87700242ffcce470d7f312a09205e6cb883 100644
--- a/Source/core/css/invalidation/StyleInvalidator.h
+++ b/Source/core/css/invalidation/StyleInvalidator.h
@@ -34,6 +34,7 @@ private:
             : m_invalidateCustomPseudo(false)
             , m_wholeSubtreeInvalid(false)
             , m_treeBoundaryCrossing(false)
+            , m_insertionPointCrossing(false)
         { }
 
         void pushInvalidationSet(const DescendantInvalidationSet&);
@@ -44,12 +45,14 @@ private:
         void setWholeSubtreeInvalid() { m_wholeSubtreeInvalid = true; }
 
         bool treeBoundaryCrossing() const { return m_treeBoundaryCrossing; }
+        bool insertionPointCrossing() const { return m_insertionPointCrossing; }
 
         typedef Vector<const DescendantInvalidationSet*, 16> InvalidationSets;
         InvalidationSets m_invalidationSets;
         bool m_invalidateCustomPseudo;
         bool m_wholeSubtreeInvalid;
         bool m_treeBoundaryCrossing;
+        bool m_insertionPointCrossing;
     };
 
     bool invalidate(Element&, RecursionData&);
@@ -63,6 +66,7 @@ private:
             , m_prevInvalidateCustomPseudo(data->m_invalidateCustomPseudo)
             , m_prevWholeSubtreeInvalid(data->m_wholeSubtreeInvalid)
             , m_treeBoundaryCrossing(data->m_treeBoundaryCrossing)
+            , m_insertionPointCrossing(data->m_insertionPointCrossing)
             , m_data(data)
         { }
         ~RecursionCheckpoint()
@@ -71,6 +75,7 @@ private:
             m_data->m_invalidateCustomPseudo = m_prevInvalidateCustomPseudo;
             m_data->m_wholeSubtreeInvalid = m_prevWholeSubtreeInvalid;
             m_data->m_treeBoundaryCrossing = m_treeBoundaryCrossing;
+            m_data->m_insertionPointCrossing = m_insertionPointCrossing;
         }
 
     private:
@@ -78,6 +83,7 @@ private:
         bool m_prevInvalidateCustomPseudo;
         bool m_prevWholeSubtreeInvalid;
         bool m_treeBoundaryCrossing;
+        bool m_insertionPointCrossing;
         RecursionData* m_data;
     };