add Brian's fiddle as gm/bicubic

Change-Id: I748ab57274c360261e957d43a08366e62350110b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263056
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

gm/bicubic.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm/gm.h"
+#include "include/core/SkBitmap.h"
+#include "include/core/SkCanvas.h"
+
+DEF_SIMPLE_GM(bicubic, canvas, 300, 64) {
+    canvas->clear(SK_ColorBLACK);
+
+    SkBitmap bmp;
+    bmp.allocN32Pixels(8, 1);
+    bmp.eraseColor(0);
+    *bmp.getAddr32(3, 0) = 0xFFFFFFFF;
+
+    SkPaint paint;
+    paint.setFilterQuality(kHigh_SkFilterQuality);
+
+    for (int i = 0; i < 64; ++i) {
+        float x = 1.0f + i/63.0f;
+        float y = i;
+        canvas->drawBitmapRect(bmp, SkRect::MakeXYWH(x, y, 512, 1), &paint);
+    }
+}

gn/gm.gni

@@ -31,6 +31,7 @@ gm_sources = [
   "$_gm/badpaint.cpp",
   "$_gm/beziereffects.cpp",
   "$_gm/beziers.cpp",
+  "$_gm/bicubic.cpp",
   "$_gm/bigblurs.cpp",
   "$_gm/bigmatrix.cpp",
   "$_gm/bigrect.cpp",