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

gm/bitmapshader.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 "gm.h"
 
 #include "SkBitmap.h"
 #include "SkPaint.h"
 #include "SkShader.h"
 
 namespace skiagm {
 
 static void draw_bm(SkBitmap* bm) {
     SkPaint bluePaint;
     bluePaint.setColor(SK_ColorBLUE);
 
-    bm->setConfig(SkBitmap::kARGB_8888_Config, 20, 20);
-    bm->allocPixels();
+    bm->allocN32Pixels(20, 20);
     bm->eraseColor(SK_ColorRED);
 
     SkCanvas canvas(*bm);
     canvas.drawCircle(10, 10, 5, bluePaint);
 }
 
 static void draw_mask(SkBitmap* bm) {
     SkPaint circlePaint;
     circlePaint.setColor(SK_ColorBLACK);
 
-    bm->setConfig(SkBitmap::kA8_Config, 20, 20);
-    bm->allocPixels();
+    bm->allocConfigPixels(SkBitmap::kA8_Config, 20, 20);
     bm->eraseColor(SK_ColorTRANSPARENT);
 
     SkCanvas canvas(*bm);
     canvas.drawCircle(10, 10, 10, circlePaint);
 }
 
 class BitmapShaderGM : public GM {
 public:
 
     BitmapShaderGM() {
@@ skipping 50 matching lines @@
 
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new BitmapShaderGM; }
 static GMRegistry reg(MyFactory);
 
 }