Switch new SkImageFilter internal methods over to sk_sp

include/effects/SkMergeImageFilter.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 SkMergeImageFilter_DEFINED
 #define SkMergeImageFilter_DEFINED
 
@@ skipping 17 matching lines @@
                                  const SkXfermode::Mode modes[] = NULL,
                                 const CropRect* cropRect = NULL) {
         return new SkMergeImageFilter(filters, count, modes, cropRect);
     }
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkMergeImageFilter)
 
 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;
 
 private:
     SkMergeImageFilter(SkImageFilter* filters[], int count, const SkXfermode::Mode modes[],
                        const CropRect* cropRect);
 
     uint8_t*    fModes; // SkXfermode::Mode
 
     // private storage, to avoid dynamically allocating storage for our copy
     // of the modes (unless the count is so large we can't fit).
     intptr_t    fStorage[16];
 
     void initAllocModes();
     void initModes(const SkXfermode::Mode []);
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif