blink: Cleanup core class forward declarations

third_party/WebKit/Source/core/timing/DOMWindowPerformance.h

 // Copyright 2015 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 DOMWindowPerformance_h
 #define DOMWindowPerformance_h
 
 #include "core/CoreExport.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
 class DOMWindow;
+class LocalDOMWindow;
 class Performance;
 
 class CORE_EXPORT DOMWindowPerformance final
     : public GarbageCollected<DOMWindowPerformance>,
       public Supplement<LocalDOMWindow>,
       public DOMWindowProperty {
   USING_GARBAGE_COLLECTED_MIXIN(DOMWindowPerformance);
   WTF_MAKE_NONCOPYABLE(DOMWindowPerformance);
 
  public:
   static DOMWindowPerformance& from(LocalDOMWindow&);
   static Performance* performance(DOMWindow&);
 
   DECLARE_TRACE();
 
  private:
   explicit DOMWindowPerformance(LocalDOMWindow&);
   static const char* supplementName();
 
   Performance* performance();
 
   // TODO(sof): try to move this direct reference and instead rely on frame().
   Member<LocalDOMWindow> m_window;
   Member<Performance> m_performance;
 };
 
 }  // namespace blink
 
 #endif  // DOMWindowPerformance_h