Rename the Custom Elements runtime feature to "CustomElements".

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 df2a96860f6c8d1425fde3bbbdebdf3d77a1d197..17be50934e802167f0309db671fffb16276ae2de 100644
--- a/Source/core/css/CSSSelector.cpp
+++ b/Source/core/css/CSSSelector.cpp
@@ -431,7 +431,7 @@ static HashMap<StringImpl*, CSSSelector::PseudoType>* nameToPseudoTypeMap()
             nameToPseudoType->set(hostWithParams.impl(), CSSSelector::PseudoHost);
             nameToPseudoType->set(content.impl(), CSSSelector::PseudoContent);
         }
-        if (RuntimeEnabledFeatures::customDOMElementsEnabled())
+        if (RuntimeEnabledFeatures::customElementsEnabled())
             nameToPseudoType->set(unresolved.impl(), CSSSelector::PseudoUnresolved);
     }
     return nameToPseudoType;