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

gm/morphology.cpp

 /*
  * Copyright 2012 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 "SkMorphologyImageFilter.h"
 
 #define WIDTH 700
 #define HEIGHT 560
 
 namespace skiagm {
 
 class MorphologyGM : public GM {
 public:
     MorphologyGM() {
         this->setBGColor(0xFF000000);
         fOnce = false;
     }
 
 protected:
     virtual SkString onShortName() {
         return SkString("morphology");
     }
 
     void make_bitmap() {
-        fBitmap.setConfig(SkBitmap::kARGB_8888_Config, 135, 135);
-        fBitmap.allocPixels();
+        fBitmap.allocN32Pixels(135, 135);
         SkBitmapDevice device(fBitmap);
         SkCanvas canvas(&device);
         canvas.clear(0x0);
         SkPaint paint;
         paint.setAntiAlias(true);
         const char* str1 = "ABC";
         const char* str2 = "XYZ";
         paint.setColor(0xFFFFFFFF);
         paint.setTextSize(64);
         canvas.drawText(str1, strlen(str1), 10, 55, paint);
@@ skipping 57 matching lines @@
     SkBitmap fBitmap;
     bool fOnce;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new MorphologyGM; }
 static GMRegistry reg(MyFactory);
 
 }