use special-image for imagefilters and save/restore layer

include/core/SkDevice.h

Index: include/core/SkDevice.h
diff --git a/include/core/SkDevice.h b/include/core/SkDevice.h
index e960003f9ac105240e8e6e41f44ee445f0a6fe12..32cdb4274192d81605f05c5900793e284a1d2f4a 100644
--- a/include/core/SkDevice.h
+++ b/include/core/SkDevice.h
@@ -22,6 +22,7 @@ struct SkIRect;
 class SkMatrix;
 class SkMetaData;
 class SkRegion;
+class SkSpecialImage;
 class GrRenderTarget;
 
 class SK_API SkBaseDevice : public SkRefCnt {
@@ -276,6 +277,11 @@ protected:
     virtual void drawTextRSXform(const SkDraw&, const void* text, size_t len, const SkRSXform[],
                                  const SkPaint&);
 
+    virtual void drawSpecial(const SkDraw&, SkSpecialImage*, int x, int y, const SkPaint&);
+    virtual sk_sp<SkSpecialImage> makeSpecial(const SkBitmap&);
+    virtual sk_sp<SkSpecialImage> makeSpecial(const SkImage*);
+    virtual sk_sp<SkSpecialImage> asSpecial();
+
     bool readPixels(const SkImageInfo&, void* dst, size_t rowBytes, int x, int y);
 
     ///////////////////////////////////////////////////////////////////////////