Remove forward declarations from Source/core/dom/custom

Source/core/dom/custom/CustomElementScheduler.h

Index: Source/core/dom/custom/CustomElementScheduler.h
diff --git a/Source/core/dom/custom/CustomElementScheduler.h b/Source/core/dom/custom/CustomElementScheduler.h
index 976679d41b1c27436e4d1b6af062e53b637a2743..8912a51adf59cba4886f93e8eb9359d000fc6b4e 100644
--- a/Source/core/dom/custom/CustomElementScheduler.h
+++ b/Source/core/dom/custom/CustomElementScheduler.h
@@ -45,8 +45,6 @@ class CustomElementDescriptor;
 class CustomElementMicrotaskImportStep;
 class CustomElementMicrotaskStep;
 class CustomElementRegistrationContext;
-class Document;
-class Element;
 class HTMLImportChild;
 
 class CustomElementScheduler FINAL : public NoBaseWillBeGarbageCollected<CustomElementScheduler> {
@@ -68,6 +66,6 @@ private:
     static void enqueueMicrotaskStep(Document&, PassOwnPtrWillBeRawPtr<CustomElementMicrotaskStep>, bool importIsSync = true);
 };
 
-}
+} // namespace blink
 
 #endif // CustomElementScheduler_h