Remove forward declarations from Source/core/dom/custom

Source/core/dom/custom/CustomElementMicrotaskDispatcher.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CustomElementMicrotaskDispatcher_h
 #define CustomElementMicrotaskDispatcher_h
 
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class CustomElementCallbackQueue;
-class CustomElementMicrotaskImportStep;
-class CustomElementMicrotaskStep;
-class Document;
-class HTMLImportLoader;
 
 class CustomElementMicrotaskDispatcher FINAL : public NoBaseWillBeGarbageCollected<CustomElementMicrotaskDispatcher> {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskDispatcher);
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CustomElementMicrotaskDispatcher);
 public:
     static CustomElementMicrotaskDispatcher& instance();
 
     void enqueue(CustomElementCallbackQueue*);
 
     bool elementQueueIsEmpty() { return m_elements.isEmpty(); }
@@ skipping 12 matching lines @@
     bool m_hasScheduledMicrotask;
     enum {
         Quiescent,
         Resolving,
         DispatchingCallbacks
     } m_phase;
 
     WillBeHeapVector<RawPtrWillBeMember<CustomElementCallbackQueue> > m_elements;
 };
 
-}
+} // namespace blink
 
 #endif // CustomElementMicrotaskDispatcher_h