Disentangle filter content recording state from FilterData

Source/core/paint/SVGFilterPainter.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SVGFilterPainter_h
 #define SVGFilterPainter_h
 
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/paint/DisplayItemList.h"
+#include "wtf/OwnPtr.h"
+
 namespace blink {
 
-class GraphicsContext;
+class FilterData;
 class LayoutObject;
 class LayoutSVGResourceFilter;
 
+class SVGFilterRecordingContext {
+public:
+    explicit SVGFilterRecordingContext(GraphicsContext* initialContext) : m_initialContext(initialContext) { }
+
+    GraphicsContext* beginContent(FilterData*);
+    void endContent(FilterData*);
+
+    GraphicsContext* paintingContext() const { return m_initialContext; }
+
+private:
+    OwnPtr<DisplayItemList> m_displayItemList;
+    OwnPtr<GraphicsContext> m_context;
+    GraphicsContext* m_initialContext;
+};
+
 class SVGFilterPainter {
 public:
     SVGFilterPainter(LayoutSVGResourceFilter& filter) : m_filter(filter) { }
 
     // Returns the context that should be used to paint the filter contents, or
     // null if the content should not be recorded.
-    GraphicsContext* prepareEffect(LayoutObject&, GraphicsContext*);
-    void finishEffect(LayoutObject&, GraphicsContext*);
+    GraphicsContext* prepareEffect(LayoutObject&, SVGFilterRecordingContext&);
+    void finishEffect(LayoutObject&, SVGFilterRecordingContext&);
 
 private:
     LayoutSVGResourceFilter& m_filter;
 };
 
 } // namespace blink
 
 #endif // SVGFilterPainter_h