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

gm/imagefiltersscaled.cpp

 /*
  * Copyright 2014 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 "SkColor.h"
 #include "SkBitmapSource.h"
@@ skipping 15 matching lines @@
 protected:
     virtual SkString onShortName() {
         return SkString("imagefiltersscaled");
     }
 
     virtual SkISize onISize() {
         return make_isize(860, 500);
     }
 
     void make_checkerboard() {
-        fCheckerboard.setConfig(SkBitmap::kARGB_8888_Config, 64, 64);
-        fCheckerboard.allocPixels();
+        fCheckerboard.allocN32Pixels(64, 64);
         SkBitmapDevice device(fCheckerboard);
         SkCanvas canvas(&device);
         canvas.clear(0x00000000);
         SkPaint darkPaint;
         darkPaint.setColor(0xFF404040);
         SkPaint lightPaint;
         lightPaint.setColor(0xFFA0A0A0);
         for (int y = 0; y < 64; y += 16) {
           for (int x = 0; x < 64; x += 16) {
             canvas.save();
             canvas.translate(SkIntToScalar(x), SkIntToScalar(y));
             canvas.drawRect(SkRect::MakeXYWH(0, 0, 8, 8), darkPaint);
             canvas.drawRect(SkRect::MakeXYWH(8, 0, 8, 8), lightPaint);
             canvas.drawRect(SkRect::MakeXYWH(0, 8, 8, 8), lightPaint);
             canvas.drawRect(SkRect::MakeXYWH(8, 8, 8, 8), darkPaint);
             canvas.restore();
           }
         }
     }
 
     void make_gradient_circle(int width, int height) {
         SkScalar x = SkIntToScalar(width / 2);
         SkScalar y = SkIntToScalar(height / 2);
         SkScalar radius = SkScalarMul(SkMinScalar(x, y), SkIntToScalar(4) / SkIntToScalar(5));
-        fGradientCircle.setConfig(SkBitmap::kARGB_8888_Config, width, height);
-        fGradientCircle.allocPixels();
+        fGradientCircle.allocN32Pixels(width, height);
         SkBitmapDevice device(fGradientCircle);
         SkCanvas canvas(&device);
         canvas.clear(0x00000000);
         SkColor colors[2];
         colors[0] = SK_ColorWHITE;
         colors[1] = SK_ColorBLACK;
         SkAutoTUnref<SkShader> shader(
             SkGradientShader::CreateRadial(SkPoint::Make(x, y), radius, colors, NULL, 2,
                                            SkShader::kClamp_TileMode)
         );
@@ skipping 69 matching lines @@
     SkBitmap fGradientCircle;
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new ImageFiltersScaledGM; }
 static GMRegistry reg(MyFactory);
 
 }