detect when we can filter bitmaps/images directly, w/o a tmp layer

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 37 matching lines @@
     virtual GrTexture* asTextureRef(GrContext*, const GrTextureParams&) const = 0;
 
     virtual SkImage* onNewSubset(const SkIRect&) const = 0;
 
     virtual SkData* onRefEncoded() 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...
+    virtual bool asBitmapForImageFilters(SkBitmap* bitmap) const {
+        return this->getROPixels(bitmap, kAllow_CachingHint);
+    }
+
     // Call when this image is part of the key to a resourcecache entry. This allows the cache
     // to know automatically those entries can be purged when this SkImage deleted.
     void notifyAddedToCache() const {
         fAddedToCache.store(true);
     }
 
 private:
     // Set true by caches when they cache content that's derived from the current pixels.
     mutable SkAtomic<bool> fAddedToCache;
 
     typedef SkImage INHERITED;
 };
 
 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