Fix nearly-vertical gradient assert

tests/GradientTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkColorShader.h"
 #include "SkGradientShader.h"
 #include "SkShader.h"
+#include "SkSurface.h"
 #include "SkTemplates.h"
 #include "Test.h"
 
 // https://code.google.com/p/chromium/issues/detail?id=448299
 // Giant (inverse) matrix causes overflow when converting/computing using 32.32
 // Before the fix, we would assert (and then crash).
 static void test_big_grad(skiatest::Reporter* reporter) {
     const SkColor colors[] = { SK_ColorRED, SK_ColorBLUE };
     const SkPoint pts[] = {{ 15, 14.7112684f }, { 0.709064007f, 12.6108112f }};
     SkShader* s = SkGradientShader::CreateLinear(pts, colors, nullptr, 2, SkShader::kClamp_TileMode);
@@ skipping 167 matching lines @@
         radial_gradproc,
         sweep_gradproc,
         conical_gradproc,
     };
 
     for (size_t i = 0; i < SK_ARRAY_COUNT(gProcs); ++i) {
         gProcs[i](reporter, rec);
     }
 }
 
+static void test_nearly_vertical(skiatest::Reporter* reporter) {
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(200, 200));
+
+    const SkPoint pts[] = {{ 100, 50 }, { 100.0001f, 50000 }};
+    const SkColor colors[] = { SK_ColorBLACK, SK_ColorWHITE };
+    const SkScalar pos[] = { 0, 1 };
+    SkAutoTUnref<SkShader> gradient(
+        SkGradientShader::CreateLinear(pts, colors, pos, 2, SkShader::kClamp_TileMode));
+
+    SkPaint paint;
+    paint.setShader(gradient);
+
+    surface->getCanvas()->drawPaint(paint);
+}
+
 DEF_TEST(Gradient, reporter) {
     TestGradientShaders(reporter);
     TestConstantGradient(reporter);
     test_big_grad(reporter);
+    test_nearly_vertical(reporter);
 }