Reduce forward declarations in core/dom

Source/core/dom/shadow/ComposedTreeWalker.h

 /*
  * Copyright (C) 2012 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.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 16 matching lines @@
 #ifndef ComposedTreeWalker_h
 #define ComposedTreeWalker_h
 
 #include "core/dom/NodeRenderingTraversal.h"
 #include "core/dom/shadow/InsertionPoint.h"
 #include "core/dom/shadow/ShadowRoot.h"
 
 namespace WebCore {
 
 class Node;
-class ShadowRoot;
 
 // FIXME: Make some functions inline to optimise the performance.
 // https://bugs.webkit.org/show_bug.cgi?id=82702
 class ComposedTreeWalker {
     STACK_ALLOCATED();
 public:
     typedef NodeRenderingTraversal::ParentDetails ParentTraversalDetails;
 
     enum StartPolicy {
         CanStartFromShadowBoundary,
@@ skipping 159 matching lines @@
 
 inline Node* ComposedTreeWalker::traverseLastChild(const Node* node) const
 {
     ASSERT(node);
     return traverseChild(node, TraversalDirectionBackward);
 }
 
 } // namespace
 
 #endif