Disentangle filter content recording state from FilterData

Source/core/svg/SVGImageElement.h

Index: Source/core/svg/SVGImageElement.h
diff --git a/Source/core/svg/SVGImageElement.h b/Source/core/svg/SVGImageElement.h
index e799c1646c5af9708d775304ab482043ad780784..6b5421f24d1bb669166ee56f0b155b345321be5e 100644
--- a/Source/core/svg/SVGImageElement.h
+++ b/Source/core/svg/SVGImageElement.h
@@ -48,6 +48,9 @@ public:
     SVGAnimatedLength* height() const { return m_height.get(); }
     SVGAnimatedPreserveAspectRatio* preserveAspectRatio() { return m_preserveAspectRatio.get(); }
 
+    // Exposed for testing.
+    ImageResource* cachedImage() const { return imageLoader().image(); }
+
 private:
     explicit SVGImageElement(Document&);
 
@@ -70,7 +73,7 @@ private:
 
     virtual bool selfHasRelativeLengths() const override;
     virtual void didMoveToNewDocument(Document& oldDocument) override;
-    SVGImageLoader& imageLoader() { return *m_imageLoader; }
+    SVGImageLoader& imageLoader() const { return *m_imageLoader; }
 
     RefPtrWillBeMember<SVGAnimatedLength> m_x;
     RefPtrWillBeMember<SVGAnimatedLength> m_y;