Clean up forward declarations in Source/core

Source/core/animation/DocumentAnimations.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
  */
 
 #ifndef DocumentAnimations_h
 #define DocumentAnimations_h
 
 #include "core/CSSPropertyNames.h"
 
 namespace blink {
 
 class Document;
-class FrameView;
 class Node;
 
 class DocumentAnimations {
 public:
     static void updateAnimationTimingForAnimationFrame(Document&, double monotonicAnimationStartTime);
     static bool needsOutdatedAnimationPlayerUpdate(const Document&);
     static void updateOutdatedAnimationPlayersIfNeeded(Document&);
     static void updateAnimationTimingForGetComputedStyle(Node&, CSSPropertyID);
     static void startPendingAnimations(Document&);
 
 private:
     DocumentAnimations() { }
 };
 
 } // namespace
 
 #endif