GM: add fadefilter gm

gm/fadefilter.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 "SkColorMatrixFilter.h"
+#include "SkColorFilterImageFilter.h"
+
+// This GM renders correctly in 8888, but fails in PDF
+DEF_SIMPLE_GM(fadefilter, canvas, 256, 256) {
+    SkScalar matrix[20] = { 1, 0, 0, 0, 128.0f,
+                            0, 1, 0, 0, 128.0f,
+                            0, 0, 1, 0, 128.0f,
+                            0, 0, 0, 1, 0 };
+    SkAutoTUnref<SkColorFilter> colorFilter(
+            SkColorMatrixFilter::Create(matrix));
+    SkAutoTUnref<SkImageFilter> filter(
+            SkColorFilterImageFilter::Create(colorFilter));
+    SkPaint layerPaint;
+    layerPaint.setImageFilter(filter);
+    canvas->drawRect(SkRect::MakeLTRB(64, 64, 192, 192), layerPaint);
+}