Fix bounds check in grshape test

tests/GrShapeTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <initializer_list>
 #include <functional>
 #include "Test.h"
@@ skipping 19 matching lines @@
     return true;
 }
 
 static bool paths_fill_same(const SkPath& a, const SkPath& b) {
     SkPath pathXor;
     Op(a, b, SkPathOp::kXOR_SkPathOp, &pathXor);
     return pathXor.isEmpty();
 }
 
 static bool test_bounds_by_rasterizing(const SkPath& path, const SkRect& bounds) {
+    // We test the bounds by rasterizing the path into a kRes by kRes grid. The bounds is
+    // mapped to the range kRes/4 to 3*kRes/4 in x and y. A difference clip is used to avoid
+    // rendering within the bounds (with a tolerance). Then we render the path and check that
+    // everything got clipped out.
     static constexpr int kRes = 2000;
     // This tolerance is in units of 1/kRes fractions of the bounds width/height.
     static constexpr int kTol = 0;
     GR_STATIC_ASSERT(kRes % 4 == 0);
     SkImageInfo info = SkImageInfo::MakeA8(kRes, kRes);
     sk_sp<SkSurface> surface = SkSurface::MakeRaster(info);
     surface->getCanvas()->clear(0x0);
     SkRect clip = SkRect::MakeXYWH(kRes/4, kRes/4, kRes/2, kRes/2);
     SkMatrix matrix;
     matrix.setRectToRect(bounds, clip, SkMatrix::kFill_ScaleToFit);
     clip.outset(SkIntToScalar(kTol), SkIntToScalar(kTol));
     surface->getCanvas()->clipRect(clip, SkRegion::kDifference_Op);
     surface->getCanvas()->concat(matrix);
     SkPaint whitePaint;
     whitePaint.setColor(SK_ColorWHITE);
     surface->getCanvas()->drawPath(path, whitePaint);
     SkPixmap pixmap;
     surface->getCanvas()->peekPixels(&pixmap);
 #if defined(SK_BUILD_FOR_WIN)
     // The static constexpr version in #else causes cl.exe to crash.
     const uint8_t* kZeros = reinterpret_cast<uint8_t*>(calloc(kRes, 1));
 #else
     static constexpr uint8_t kZeros[kRes] = {0};
 #endif
-    for (int y = 0; y < kRes/4; ++y) {
+    for (int y = 0; y < kRes; ++y) {
         const uint8_t* row = pixmap.addr8(0, y);
         if (0 != memcmp(kZeros, row, kRes)) {
             return false;
         }
     }
 #ifdef SK_BUILD_FOR_WIN
     free(const_cast<uint8_t*>(kZeros));
 #endif
     return true;
 }
@@ skipping 1811 matching lines @@
     test_volatile_path(reporter, PathGeo(SkPath(), PathGeo::Invert::kNo));
 
     test_empty_shape(reporter);
 
     test_lines(reporter);
 
     test_stroked_lines(reporter);
 }
 
 #endif