add runtime option to provide data->imagegenerator factory

src/lazy/SkDiscardablePixelRef.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDiscardablePixelRef.h"
 #include "SkDiscardableMemory.h"
 #include "SkImageGenerator.h"
@@ skipping 132 matching lines @@
     return true;
 }
 
 // These are the public API
 
 bool SkInstallDiscardablePixelRef(SkImageGenerator* generator, SkBitmap* dst) {
     return SkInstallDiscardablePixelRef(generator, NULL, dst, NULL);
 }
 
 bool SkInstallDiscardablePixelRef(SkData* encoded, SkBitmap* dst) {
-    SkImageGenerator* generator = SkImageGenerator::NewFromData(encoded);
+    SkImageGenerator* generator = SkImageGenerator::NewFromEncoded(encoded);
     return generator ? SkInstallDiscardablePixelRef(generator, NULL, dst, NULL) : false;
 }