SkImage_Raster's pixels are always immutable.

tests/DeferredCanvasTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "../src/image/SkImagePriv.h"
 #include "../src/image/SkSurface_Base.h"
 #include "SkBitmap.h"
@@ skipping 46 matching lines @@
 
     SkCanvas* onNewCanvas() override {
         return SkNEW_ARGS(SkCanvas, (fBitmap));
     }
 
     SkSurface* onNewSurface(const SkImageInfo&) override {
         return NULL;
     }
 
     SkImage* onNewImageSnapshot(Budgeted) override {
-        return SkNewImageFromRasterBitmap(fBitmap, true, &this->props(),
-                                          kUnlocked_SharedPixelRefMode);
+        return SkNewImageFromRasterBitmap(fBitmap, &this->props(), kUnlocked_SharedPixelRefMode);
     }
 
     void onCopyOnWrite(ContentChangeMode mode) override {
         if (mode == SkSurface::kDiscard_ContentChangeMode) {
             fCOWDiscardCount++;
         } else {
             fCOWRetainCount++;
         }
     }
 
@@ skipping 861 matching lines @@
     TestDeferredCanvasSurface(reporter, NULL);
     TestDeferredCanvasSetSurface(reporter, NULL);
 }
 
 DEF_GPUTEST(DeferredCanvas_GPU, reporter, factory) {
     if (factory != NULL) {
         TestDeferredCanvasSurface(reporter, factory);
         TestDeferredCanvasSetSurface(reporter, factory);
     }
 }