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

gm/optimizations.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 "SkDebugCanvas.h"
 #include "SkPictureFlat.h"
@@ skipping 377 matching lines @@
             // TODO: we could also render the pre and post pictures to bitmaps
             // and manually compare them in this method
         }
     }
 
 private:
     void makeCheckerboard() {
         static const unsigned int kCheckerboardWidth = 16;
         static const unsigned int kCheckerboardHeight = 16;
 
-        fCheckerboard.setConfig(SkBitmap::kARGB_8888_Config,
-                                kCheckerboardWidth, kCheckerboardHeight);
-        fCheckerboard.allocPixels();
-        SkAutoLockPixels lock(fCheckerboard);
+        fCheckerboard.allocN32Pixels(kCheckerboardWidth, kCheckerboardHeight);
         for (unsigned int y = 0; y < kCheckerboardHeight; y += 2) {
             SkPMColor* scanline = fCheckerboard.getAddr32(0, y);
             for (unsigned int x = 0; x < kCheckerboardWidth; x += 2) {
                 *scanline++ = 0xFFFFFFFF;
                 *scanline++ = 0xFF000000;
             }
             scanline = fCheckerboard.getAddr32(0, y + 1);
             for (unsigned int x = 0; x < kCheckerboardWidth; x += 2) {
                 *scanline++ = 0xFF000000;
                 *scanline++ = 0xFFFFFFFF;
             }
         }
     }
 
     SkBitmap fCheckerboard;
 
     typedef skiagm::GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new OptimizationsGM; )