Implement ::content

Source/core/css/CSSGrammar.y.in

Index: Source/core/css/CSSGrammar.y.in
diff --git a/Source/core/css/CSSGrammar.y.in b/Source/core/css/CSSGrammar.y.in
index adcd2ad93e2d82af194a4152ad84923b02f2b411..4ef806b423fb4d4ad2c92984a2619354c95c6f6b 100644
--- a/Source/core/css/CSSGrammar.y.in
+++ b/Source/core/css/CSSGrammar.y.in
@@ -1182,6 +1182,8 @@ selector:
         while (end->tagHistory())
             end = end->tagHistory();
         end->setRelation(CSSSelector::Descendant);
+        if ($1->isContentPseudoElement())
+            end->setRelationIsAffectedByPseudoContent();
         end->setTagHistory(parser->sinkFloatingSelector($1));
     }
     | selector combinator simple_selector {
@@ -1190,6 +1192,8 @@ selector:
         while (end->tagHistory())
             end = end->tagHistory();
         end->setRelation($2);
+        if ($1->isContentPseudoElement())
+            end->setRelationIsAffectedByPseudoContent();
         end->setTagHistory(parser->sinkFloatingSelector($1));
     }
     ;