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

gm/bleed.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 "SkBlurMask.h"
 #include "SkBlurMaskFilter.h"
 #include "SkCanvas.h"
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #endif
 
 // Create a black&white checked texture with 2 1-pixel rings
 // around the outside edge. The inner ring is red and the outer ring is blue.
 static void make_ringed_bitmap(SkBitmap* result, int width, int height) {
     SkASSERT(0 == width % 2 && 0 == height % 2);
 
     static const SkPMColor kRed = SkPreMultiplyColor(SK_ColorRED);
     static const SkPMColor kBlue = SkPreMultiplyColor(SK_ColorBLUE);
     static const SkPMColor kBlack = SkPreMultiplyColor(SK_ColorBLACK);
     static const SkPMColor kWhite = SkPreMultiplyColor(SK_ColorWHITE);
 
-    result->setConfig(SkBitmap::kARGB_8888_Config, width, height, 0,
-                      kOpaque_SkAlphaType);
-    result->allocPixels();
-    SkAutoLockPixels lock(*result);
+    result->allocN32Pixels(width, height, true);
 
     SkPMColor* scanline = result->getAddr32(0, 0);
     for (int x = 0; x < width; ++x) {
         scanline[x] = kBlue;
     }
     scanline = result->getAddr32(0, 1);
     scanline[0] = kBlue;
     for (int x = 1; x < width - 1; ++x) {
         scanline[x] = kRed;
     }
@@ skipping 231 matching lines @@
     static const int kSmallTextureSize = 6;
     static const int kMaxTextureSize = 32;
 
     SkBitmap fBitmapSmall;
     SkBitmap fBitmapBig;
 
     typedef GM INHERITED;
 };
 
 DEF_GM( return new BleedGM(); )