Support style invalidation for ::content.

Source/core/css/RuleFeature.cpp

Index: Source/core/css/RuleFeature.cpp
diff --git a/Source/core/css/RuleFeature.cpp b/Source/core/css/RuleFeature.cpp
index 69ea193992b9bec69ff3659e3801a1fd1dbc4775..bc75b5266a72013a3ab7af5b09c553a65a429748 100644
--- a/Source/core/css/RuleFeature.cpp
+++ b/Source/core/css/RuleFeature.cpp
@@ -53,6 +53,7 @@ static bool isSkippableComponentForInvalidation(const CSSSelector& selector)
         case CSSSelector::PseudoAfter:
         case CSSSelector::PseudoBackdrop:
         case CSSSelector::PseudoShadow:
+        case CSSSelector::PseudoContent:
             return true;
         default:
             ASSERT(!selector.isCustomPseudoElement());
@@ -288,6 +289,8 @@ void RuleFeatureSet::addFeaturesToInvalidationSet(DescendantInvalidationSet& inv
 {
     if (features.treeBoundaryCrossing)
         invalidationSet.setTreeBoundaryCrossing();
+    if (features.insertionPointCrossing)
+        invalidationSet.setInsertionPointCrossing();
     if (features.adjacent) {
         invalidationSet.setWholeSubtreeInvalid();
         return;
@@ -310,8 +313,10 @@ void RuleFeatureSet::addFeaturesToInvalidationSets(const CSSSelector& selector,
         if (DescendantInvalidationSet* invalidationSet = invalidationSetForSelector(*current)) {
             addFeaturesToInvalidationSet(*invalidationSet, features);
         } else {
-            if (current->pseudoType() == CSSSelector::PseudoHost)
+            if (current->isTreeBoundaryCrossing())
                 features.treeBoundaryCrossing = true;
+            if (current->isInsertionPointCrossing())
+                features.insertionPointCrossing = true;
             if (const CSSSelectorList* selectorList = current->selectorList()) {
                 ASSERT(current->pseudoType() == CSSSelector::PseudoHost || current->pseudoType() == CSSSelector::PseudoAny || current->pseudoType() == CSSSelector::PseudoNot);
                 for (const CSSSelector* selector = selectorList->first(); selector; selector = CSSSelectorList::next(*selector))