Switch new SkImageFilter internal methods over to sk_sp

include/effects/SkImageSource.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageSource_DEFINED
 #define SkImageSource_DEFINED
 
@@ skipping 10 matching lines @@
                                  SkFilterQuality);
 
     SkRect computeFastBounds(const SkRect& src) const override;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkImageSource)
 
 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:
     explicit SkImageSource(SkImage*);
     SkImageSource(SkImage*,
                   const SkRect& srcRect,
                   const SkRect& dstRect,
                   SkFilterQuality);
 
     sk_sp<SkImage>   fImage;
     SkRect           fSrcRect, fDstRect;
     SkFilterQuality  fFilterQuality;
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif