tweak mipmap_srgb gm to use integer coordinates

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 52 matching lines @@
         }
     }
     bm.setImmutable();
     return SkImage::MakeFromBitmap(bm);
 }
 
 static void show_mips(SkCanvas* canvas, SkImage* img) {
     SkPaint paint;
     paint.setFilterQuality(kMedium_SkFilterQuality);
 
-    SkRect dst = SkRect::MakeIWH(img->width(), img->height());
+    // Want to ensure we never draw fractional pixels, so we use an IRect
+    SkIRect dst = SkIRect::MakeWH(img->width(), img->height());
     while (dst.width() > 5) {
-        canvas->drawImageRect(img, dst, &paint);
+        canvas->drawImageRect(img, SkRect::Make(dst), &paint);
         dst.offset(dst.width() + 10, 0);
-        dst.fRight = dst.fLeft + SkScalarHalf(dst.width());
-        dst.fBottom = dst.fTop + SkScalarHalf(dst.height());
+        dst.fRight = dst.fLeft + dst.width()/2;
+        dst.fBottom = dst.fTop + dst.height()/2;
     }
 }
 
 /*
  *  Ensure that in L32 drawing mode, both images/mips look the same as each other, and
  *  their mips are darker than the original (since the mips should ignore the gamma in L32).
  *
  *  Ensure that in S32 drawing mode, all images/mips look the same, and look correct (i.e.
  *  the mip levels match the original in brightness).
  */
 DEF_SIMPLE_GM(mipmap_srgb, canvas, 260, 230) {
     sk_sp<SkImage> limg = make(nullptr);
     sk_sp<SkImage> simg = make(SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named));
 
     canvas->translate(10, 10);
     show_mips(canvas, limg.get());
     canvas->translate(0, limg->height() + 10.0f);
     show_mips(canvas, simg.get());
 }