flag to use const& instead of const* for src-rect

gm/mipmap.cpp

 /*
  * Copyright 2015 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 "SkCanvas.h"
 #include "SkImage.h"
@@ skipping 24 matching lines @@
     const SkRect dst = SkRect::MakeWH(177, 15);
 
     paint.setTextSize(30);
     SkString str;
     str.printf("scale %g %g", dst.width() / img->width(), dst.height() / img->height());
 //    canvas->drawText(str.c_str(), str.size(), 300, 100, paint);
 
     canvas->translate(20, 20);
     for (int i = 0; i < 4; ++i) {
         paint.setFilterQuality(SkFilterQuality(i));
-        canvas->drawImageRect(img, NULL, dst, &paint);
+        canvas->drawImageRect(img, dst, &paint);
         canvas->translate(0, 20);
     }
     canvas->drawImage(img, 20, 20, NULL);
 }
 
 class MipMapGM : public skiagm::GM {
 public:
     MipMapGM() {}
 
 protected:
     SkString onShortName() override { return SkString("mipmap"); }
 
     SkISize onISize() override { return SkISize::Make(400, 200); }
 
     void onDraw(SkCanvas* canvas) override {
         test_mip(canvas);
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new MipMapGM; )