Reverting base class for CachedSVGDocumentReference to avoid platform layering violations

Source/WebCore/loader/cache/CachedSVGDocumentReference.h

Index: Source/WebCore/loader/cache/CachedSVGDocumentReference.h
diff --git a/Source/WebCore/loader/cache/CachedSVGDocumentReference.h b/Source/WebCore/loader/cache/CachedSVGDocumentReference.h
index 468030f8bf28ef7a3c2e976d95bea524aa977fb2..18a4e37655ec2d1977421aa87a73441733287f67 100644
--- a/Source/WebCore/loader/cache/CachedSVGDocumentReference.h
+++ b/Source/WebCore/loader/cache/CachedSVGDocumentReference.h
@@ -29,10 +29,11 @@
 #if ENABLE(SVG) && ENABLE(CSS_FILTERS)
 #include "CachedResourceHandle.h"
 #include "CachedSVGDocument.h"
+#include "FilterOperation.h"
 
 namespace WebCore {
 
-class CachedSVGDocumentReference : public CachedSVGDocumentClient {
+class CachedSVGDocumentReference : public ReferenceFilterOperation::Data, public CachedSVGDocumentClient {
 public:
     CachedSVGDocumentReference(CachedSVGDocument* document) : m_document(document) { m_document->addClient(this); }
     virtual ~CachedSVGDocumentReference() { m_document->removeClient(this); }