add SkBitmap::installPixelRef()

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 76 matching lines @@
         || (!dst->setConfig(info, 0))) {
         return false;
     }
     SkASSERT(dst->config() != SkBitmap::kNo_Config);
     if (dst->empty()) {  // Use a normal pixelref.
         return dst->allocPixels(NULL, NULL);
     }
     SkAutoTUnref<SkDiscardablePixelRef> ref(
         SkNEW_ARGS(SkDiscardablePixelRef,
                    (info, autoGenerator.detach(), dst->rowBytes(), factory)));
-    dst->setPixelRef(ref);
+    dst->installPixelRef(ref);
     return true;
 }