Switch new SkImageFilter internal methods over to sk_sp

include/effects/SkOffsetImageFilter.h

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOffsetImageFilter_DEFINED
 #define SkOffsetImageFilter_DEFINED
 
@@ skipping 10 matching lines @@
         return new SkOffsetImageFilter(dx, dy, input, cropRect);
     }
 
     SkRect computeFastBounds(const SkRect& src) const override;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkOffsetImageFilter)
 
 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&, const SkMatrix&, MapDirection) const override;
 
 private:
     SkOffsetImageFilter(SkScalar dx, SkScalar dy, SkImageFilter* input, const CropRect*);
 
     SkVector fOffset;
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif