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

gm/pathopsinverse.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 "SkBitmap.h"
 #include "SkPath.h"
@@ skipping 18 matching lines @@
         makePaint(&fOpPaint[kIntersect_PathOp], blendColor);
         makePaint(&fOpPaint[kUnion_PathOp], 0xFFc0FFc0);
         makePaint(&fOpPaint[kReverseDifference_PathOp], twoColor);
         makePaint(&fOpPaint[kXOR_PathOp], 0xFFa0FFe0);
         makePaint(&fOutlinePaint, 0xFF000000);
         fOutlinePaint.setStyle(SkPaint::kStroke_Style);
     }
 
     SkColor blend(SkColor one, SkColor two) {
         SkBitmap temp;
-        temp.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
-        temp.allocPixels();
+        temp.allocN32Pixels(1, 1);
         SkCanvas canvas(temp);
         canvas.drawColor(one);
         canvas.drawColor(two);
         void* pixels = temp.getPixels();
         return *(SkColor*) pixels;
     }
 
     void makePaint(SkPaint* paint, SkColor color) {
         paint->setAntiAlias(true);
         paint->setStyle(SkPaint::kFill_Style);
@@ skipping 55 matching lines @@
     SkPaint fOpPaint[kReverseDifference_PathOp - kDifference_PathOp + 1];
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new PathOpsInverseGM; }
 static GMRegistry reg(MyFactory);
 
 }