Include Document.h in fewer headers

Source/core/dom/shadow/ShadowRoot.h

Index: Source/core/dom/shadow/ShadowRoot.h
diff --git a/Source/core/dom/shadow/ShadowRoot.h b/Source/core/dom/shadow/ShadowRoot.h
index 97d54a6107416057187c3105191483f6457c6359..d404d9724adbd73b5d81ac08522ec6de26b9482b 100644
--- a/Source/core/dom/shadow/ShadowRoot.h
+++ b/Source/core/dom/shadow/ShadowRoot.h
@@ -28,7 +28,6 @@
 #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"
@@ -36,11 +35,13 @@
 
 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);