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

src/image/SkImage_Base.h

Index: src/image/SkImage_Base.h
diff --git a/src/image/SkImage_Base.h b/src/image/SkImage_Base.h
index c91430e5bd4ca88b9dfcbb414bb09ec85ea6cb29..5cb6a48132c997746623c58bcba5dcbad565076f 100644
--- a/src/image/SkImage_Base.h
+++ b/src/image/SkImage_Base.h
@@ -55,6 +55,12 @@ public:
 
     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 {