Remove forward declarations from Source/core/dom/custom

Source/core/dom/custom/CustomElementSyncMicrotaskQueue.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 CustomElementSyncMicrotaskQueue_h
 #define CustomElementSyncMicrotaskQueue_h
 
 #include "core/dom/custom/CustomElementMicrotaskQueueBase.h"
 
 namespace blink {
 
 class CustomElementSyncMicrotaskQueue : public CustomElementMicrotaskQueueBase {
 public:
     static PassRefPtrWillBeRawPtr<CustomElementSyncMicrotaskQueue> create() { return adoptRefWillBeNoop(new CustomElementSyncMicrotaskQueue()); }
 
     void enqueue(PassOwnPtrWillBeRawPtr<CustomElementMicrotaskStep>);
 
 private:
     CustomElementSyncMicrotaskQueue() { }
     virtual void doDispatch();
 };
 
-}
+} // namespace blink
 
-#endif
+#endif // CustomElementSyncMicrotaskQueue_h