Support style invalidation for ::content.

Source/core/css/invalidation/StyleInvalidator.cpp

Index: Source/core/css/invalidation/StyleInvalidator.cpp
diff --git a/Source/core/css/invalidation/StyleInvalidator.cpp b/Source/core/css/invalidation/StyleInvalidator.cpp
index 8d506a5a375a70a155f346b035b20d8b69c84dbb..b3541844a4906bcfa133fb53971cc103db94d3dc 100644
--- a/Source/core/css/invalidation/StyleInvalidator.cpp
+++ b/Source/core/css/invalidation/StyleInvalidator.cpp
@@ -83,6 +83,8 @@ void StyleInvalidator::RecursionData::pushInvalidationSet(const DescendantInvali
     ASSERT(!m_wholeSubtreeInvalid);
     if (invalidationSet.treeBoundaryCrossing())
         m_treeBoundaryCrossing = true;
+    if (invalidationSet.insertionPointCrossing())
+        m_insertionPointCrossing = true;
     if (invalidationSet.wholeSubtreeInvalid()) {
         m_wholeSubtreeInvalid = true;
         return;
@@ -100,6 +102,9 @@ ALWAYS_INLINE bool StyleInvalidator::RecursionData::matchesCurrentInvalidationSe
         return true;
     }
 
+    if (m_insertionPointCrossing && element.isInsertionPoint())
+        return true;
+
     for (const auto& invalidationSet : m_invalidationSets) {
         if (invalidationSet->invalidatesElement(element))
             return true;
@@ -173,6 +178,9 @@ bool StyleInvalidator::invalidate(Element& element, StyleInvalidator::RecursionD
         }
     }
 
+    if (recursionData.insertionPointCrossing() && element.isInsertionPoint())
+        element.setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::StyleInvalidator));
+
     element.clearChildNeedsStyleInvalidation();
     element.clearNeedsStyleInvalidation();