add Make variations to return SkImage by sk_sp

src/image/SkImage_Base.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_Base_DEFINED
 #define SkImage_Base_DEFINED
 
@@ skipping 28 matching lines @@
     // but only inspect them (or encode them).
     virtual bool getROPixels(SkBitmap*, CachingHint = kAllow_CachingHint) const = 0;
 
     virtual SkSurface* onNewSurface(const SkImageInfo& info) const {
         return SkSurface::NewRaster(info);
     }
 
     // Caller must call unref when they are done.
     virtual GrTexture* asTextureRef(GrContext*, const GrTextureParams&) const = 0;
 
-    virtual SkImage* onNewSubset(const SkIRect&) const = 0;
+    virtual sk_sp<SkImage> onMakeSubset(const SkIRect&) const = 0;
 
     // If a ctx is specified, then only gpu-specific formats are requested.
     virtual SkData* onRefEncoded(GrContext*) const { return nullptr; }
 
     virtual bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const;
 
     virtual bool onIsLazyGenerated() const { return false; }
 
     // Return a bitmap suitable for passing to image-filters
     // For now, that means wrapping textures into SkGrPixelRefs...
@@ skipping 16 matching lines @@
 
 static inline SkImage_Base* as_IB(SkImage* image) {
     return static_cast<SkImage_Base*>(image);
 }
 
 static inline const SkImage_Base* as_IB(const SkImage* image) {
     return static_cast<const SkImage_Base*>(image);
 }
 
 #endif