Skia side RGB to YUV gpu conversion

src/lazy/SkDiscardablePixelRef.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDiscardablePixelRef_DEFINED
 #define SkDiscardablePixelRef_DEFINED
 
@@ skipping 18 matching lines @@
     ~SkDiscardablePixelRef();
 
     virtual bool onNewLockPixels(LockRec*) SK_OVERRIDE;
     virtual void onUnlockPixels() SK_OVERRIDE;
     virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }
 
     virtual SkData* onRefEncodedData() SK_OVERRIDE {
         return fGenerator->refEncodedData();
     }
 
+    virtual SkImageGenerator* getImageGenerator() const SK_OVERRIDE {
+        return fGenerator;
+    }
+
 private:
     SkImageGenerator* const fGenerator;
     SkDiscardableMemory::Factory* const fDMFactory;
     const size_t fRowBytes;
     // These const members should not change over the life of the
     // PixelRef, since the SkBitmap doesn't expect them to change.
 
     SkDiscardableMemory* fDiscardableMemory;
     SkAutoTUnref<SkColorTable> fCTable;
 
     /* Takes ownership of SkImageGenerator. */
     SkDiscardablePixelRef(const SkImageInfo&, SkImageGenerator*,
                           size_t rowBytes,
                           SkDiscardableMemory::Factory* factory);
 
     friend bool SkInstallDiscardablePixelRef(SkImageGenerator*, SkBitmap*,
                                              SkDiscardableMemory::Factory*);
 
     typedef SkPixelRef INHERITED;
 };
 
 #endif  // SkDiscardablePixelRef_DEFINED