Include Document.h in fewer headers

Source/core/dom/shadow/ShadowRoot.h

 /*
  * Copyright (C) 2011 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 10 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ShadowRoot_h
 #define ShadowRoot_h
 
 #include "core/dom/ContainerNode.h"
-#include "core/dom/Document.h"
 #include "core/dom/DocumentFragment.h"
 #include "core/dom/Element.h"
 #include "core/dom/TreeScope.h"
 #include "wtf/DoublyLinkedList.h"
 
 namespace WebCore {
 
+class Document;
 class ElementShadow;
 class ExceptionState;
 class HTMLShadowElement;
 class InsertionPoint;
 class ShadowRootRareData;
+class StyleSheetList;
 
 class ShadowRoot FINAL : public DocumentFragment, public TreeScope, public DoublyLinkedListNode<ShadowRoot> {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ShadowRoot);
     friend class WTF::DoublyLinkedListNode<ShadowRoot>;
 public:
     // FIXME: We will support multiple shadow subtrees, however current implementation does not work well
     // if a shadow root is dynamically created. So we prohibit multiple shadow subtrees
     // in several elements for a while.
     // See https://bugs.webkit.org/show_bug.cgi?id=77503 and related bugs.
     enum ShadowRootType {
@@ skipping 106 matching lines @@
 {
     return adjustedFocusedElement();
 }
 
 DEFINE_NODE_TYPE_CASTS(ShadowRoot, isShadowRoot());
 DEFINE_TYPE_CASTS(ShadowRoot, TreeScope, treeScope, treeScope->rootNode().isShadowRoot(), treeScope.rootNode().isShadowRoot());
 
 } // namespace
 
 #endif