SkDiscardablePixelRef should favor not decoding to YUV if they already decoded to RGB.

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 34 matching lines @@
 
     /* Takes ownership of SkImageGenerator. */
     SkDiscardablePixelRef(const SkImageInfo&, SkImageGenerator*,
                           size_t rowBytes,
                           SkDiscardableMemory::Factory* factory);
 
     virtual bool onGetYUV8Planes(SkISize sizes[3],
                                  void* planes[3],
                                  size_t rowBytes[3],
                                  SkYUVColorSpace* colorSpace) SK_OVERRIDE {
+        // If the image was already decoded with lockPixels(), favor not
+        // re-decoding to YUV8 planes.
+        if (fDiscardableMemory) {
+            return false;
+        }
         return fGenerator->getYUV8Planes(sizes, planes, rowBytes, colorSpace);
     }
 
     friend bool SkInstallDiscardablePixelRef(SkImageGenerator*, SkBitmap*,
                                              SkDiscardableMemory::Factory*);
 
     typedef SkPixelRef INHERITED;
 };
 
 #endif  // SkDiscardablePixelRef_DEFINED