take gr-context parameter to refEncoded, indicating a desire for only gpu-specific formats

src/core/SkImageCacherator.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 SkImageCacherator_DEFINED
 #define SkImageCacherator_DEFINED
 
@@ skipping 36 matching lines @@
      *  added to the cache on its behalf.
      *
      *  The caller is responsible for calling texture->unref() when they are done.
      */
     GrTexture* lockAsTexture(GrContext*, const GrTextureParams&, const SkImage* client,
                              SkImage::CachingHint = SkImage::kAllow_CachingHint);
 
     /**
      *  If the underlying src naturally is represented by an encoded blob (in SkData), this returns
      *  a ref to that data. If not, it returns null.
+     *
+     *  If a GrContext is specified, then the caller is only interested in gpu-specific encoded
+     *  formats, so others (e.g. PNG) can just return nullptr.
      */
-    SkData* refEncoded();
+    SkData* refEncoded(GrContext*);
 
     // Only return true if the generate has already been cached.
     bool lockAsBitmapOnlyIfAlreadyCached(SkBitmap*);
     // Call the underlying generator directly
     bool directGeneratePixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRB,
                               int srcX, int srcY);
 
 private:
     SkImageCacherator(SkImageGenerator*, const SkImageInfo&, const SkIPoint&, uint32_t uniqueID);
 
@@ skipping 23 matching lines @@
     SkAutoTDelete<SkImageGenerator> fNotThreadSafeGenerator;
 
     const SkImageInfo   fInfo;
     const SkIPoint      fOrigin;
     const uint32_t      fUniqueID;
 
     friend class GrImageTextureMaker;
 };
 
 #endif