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

gm/scalebitmap.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 "SkImageDecoder.h"
@@ skipping 17 matching lines @@
         SkFILEStream stream(path.c_str());
         if (stream.isValid()) {
             codec = SkImageDecoder::Factory(&stream);
         }
         if (codec) {
             stream.rewind();
             codec->decode(&stream, &fBM, SkBitmap::kARGB_8888_Config,
                 SkImageDecoder::kDecodePixels_Mode);
             SkDELETE(codec);
         } else {
-            fBM.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
-            fBM.allocPixels();
+            fBM.allocN32Pixels(1, 1);
             *(fBM.getAddr32(0,0)) = 0xFF0000FF; // red == bad
         }
         fSize = fBM.height();
     }
 
 protected:
 
 
     SkBitmap    fBM;
     SkString    fName;
     SkString    fFilename;
     int         fSize;
     float       fScale;
 
 
     virtual SkString onShortName() SK_OVERRIDE {
         return fName;
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(fBM.width() * fScale, fBM.height() * fScale);
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         SkBitmap dst;
-        dst.setConfig(SkBitmap::kARGB_8888_Config, fBM.width() * fScale, fBM.height() * fScale);
-        dst.allocPixels();
+        dst.allocN32Pixels(fBM.width() * fScale, fBM.height() * fScale);
         fBM.scale(&dst);
 
         canvas->drawBitmap(dst, 0, 0);
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 
 class ScaleBitmapMipmapGM: public ScaleBitmapGM {
@@ skipping 27 matching lines @@
 
 DEF_GM( return new ScaleBitmapGM("nature.jpg", 0.5f); )
 DEF_GM( return new ScaleBitmapGM("nature.jpg", 0.25f); )
 DEF_GM( return new ScaleBitmapGM("nature.jpg", 0.125f); )
 DEF_GM( return new ScaleBitmapGM("nature.jpg", 0.0625f); )
 
 DEF_GM( return new ScaleBitmapMipmapGM("nature.jpg", 0.5f); )
 DEF_GM( return new ScaleBitmapMipmapGM("nature.jpg", 0.25f); )
 DEF_GM( return new ScaleBitmapMipmapGM("nature.jpg", 0.125f); )
 DEF_GM( return new ScaleBitmapMipmapGM("nature.jpg", 0.0625f); )