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

src/lazy/SkDiscardablePixelRef.h

Index: src/lazy/SkDiscardablePixelRef.h
diff --git a/src/lazy/SkDiscardablePixelRef.h b/src/lazy/SkDiscardablePixelRef.h
index 448f0ab24b907c1fe7b3ce1e49146905e30f0cd3..54991ea4d1088cc9a839082c18a4fa3dc0cc1f48 100644
--- a/src/lazy/SkDiscardablePixelRef.h
+++ b/src/lazy/SkDiscardablePixelRef.h
@@ -52,6 +52,11 @@ private:
                                  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);
     }