Switch new SkImageFilter internal methods over to sk_sp

include/effects/SkDropShadowImageFilter.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDropShadowImageFilter_DEFINED
 #define SkDropShadowImageFilter_DEFINED
 
@@ skipping 18 matching lines @@
         return new SkDropShadowImageFilter(dx, dy, sigmaX, sigmaY, color, shadowMode, input,
                                            cropRect);
     }
 
     SkRect computeFastBounds(const SkRect&) const override;
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDropShadowImageFilter)
 
 protected:
     void flatten(SkWriteBuffer&) const override;
-    SkSpecialImage* onFilterImage(SkSpecialImage* source, const Context&,
-                                  SkIPoint* offset) const override;
+    sk_sp<SkSpecialImage> onFilterImage(SkSpecialImage* source, const Context&,
+                                        SkIPoint* offset) const override;
     SkIRect onFilterNodeBounds(const SkIRect& src, const SkMatrix&, MapDirection) const override;
 
 private:
     SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigmaX, SkScalar sigmaY, SkColor,
                             ShadowMode shadowMode, SkImageFilter* input, const CropRect* cropRect);
 
     SkScalar fDx, fDy, fSigmaX, fSigmaY;
     SkColor fColor;
     ShadowMode fShadowMode;
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif