add legacy/helper allocN32Pixels, and convert gm to use it

gm/extractbitmap.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "gm.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
 #include "SkString.h"
 
 namespace skiagm {
 
 static void create_bitmap(SkBitmap* bitmap) {
     const int W = 100;
     const int H = 100;
-    bitmap->setConfig(SkBitmap::kARGB_8888_Config, W, H);
-    bitmap->allocPixels();
+    bitmap->allocN32Pixels(W, H);
 
     SkCanvas canvas(*bitmap);
     canvas.drawColor(SK_ColorRED);
     SkPaint paint;
     paint.setColor(SK_ColorBLUE);
     canvas.drawCircle(SkIntToScalar(W)/2, SkIntToScalar(H)/2, SkIntToScalar(W)/2, paint);
 }
 
 class ExtractBitmapGM : public GM {
 public:
@@ skipping 64 matching lines @@
 private:
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new ExtractBitmapGM; }
 static GMRegistry reg(MyFactory);
 
 }