Remove forward declarations from Source/core/dom/custom

Source/core/dom/custom/CustomElementRegistrationContext.h

Index: Source/core/dom/custom/CustomElementRegistrationContext.h
diff --git a/Source/core/dom/custom/CustomElementRegistrationContext.h b/Source/core/dom/custom/CustomElementRegistrationContext.h
index 1acc756afdcf03a8f98a6b5e4cf641853ac67851..c79bceb34c3550394ff5041ac89ac2116f915bce 100644
--- a/Source/core/dom/custom/CustomElementRegistrationContext.h
+++ b/Source/core/dom/custom/CustomElementRegistrationContext.h
@@ -43,11 +43,6 @@
 
 namespace blink {
 
-class CustomElementConstructorBuilder;
-class Document;
-class Element;
-class ExceptionState;
-
 class CustomElementRegistrationContext FINAL : public RefCountedWillBeGarbageCollectedFinalized<CustomElementRegistrationContext> {
 public:
     static PassRefPtrWillBeRawPtr<CustomElementRegistrationContext> create()
@@ -83,7 +78,7 @@ private:
     OwnPtrWillBeMember<CustomElementUpgradeCandidateMap> m_candidates;
 };
 
-}
+} // namespace blink
 
 #endif // CustomElementRegistrationContext_h