Make a '::distributed' pseudo element the first-ever client who can accept a relative selector.

Source/core/css/CSSSelector.cpp

Index: Source/core/css/CSSSelector.cpp
diff --git a/Source/core/css/CSSSelector.cpp b/Source/core/css/CSSSelector.cpp
index e6645dfcb0af5094d9263909bdad3d7685d8762c..75d10cdb733595029849bbf8011ec47e9790490e 100644
--- a/Source/core/css/CSSSelector.cpp
+++ b/Source/core/css/CSSSelector.cpp
@@ -695,8 +695,10 @@ String CSSSelector::selectorText(const String& rightSide) const
             ASSERT_NOT_REACHED();
         case CSSSelector::ShadowPseudo:
             return tagHistory->selectorText(str.toString() + rightSide);
-        case CSSSelector::ShadowDistributed:
+        case CSSSelector::ShadowVirtualDescendant:
             return tagHistory->selectorText("::-webkit-distributed(" + str.toString() + rightSide + ")");
+        case CSSSelector::ShadowVirtualChild:
+            return tagHistory->selectorText("::-webkit-distributed(> " + str.toString() + rightSide + ")");
         }
     }
     return str.toString() + rightSide;