Add GM for filtering bug

For SkFilterQuality we get:

High   - repros for GPU
Medium - repros for both!
Low    - repros for both!
None   - doesn't repro

For AA quality (with filter quality fixed at High) we get:

AA     - repros for GPU
BW     - repros for GPU

BUG=673261

Change-Id: Ibf0644352bfa9d9c0e2d166e396ce9e9799b6d9d
Reviewed-on: https://skia-review.googlesource.com/6187
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

gm/filterbug.cpp

@@ -0,0 +1,101 @@
+/*
+ * 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 "gm.h"
+#include "SkImageShader.h"
+
+static const sk_sp<SkImage> make_image(int firstBlackRow, int lastBlackRow) {
+    static const int kWidth = 25;
+    static const int kHeight = 27;
+
+    SkBitmap bm;
+    bm.allocN32Pixels(kWidth, kHeight);
+    bm.eraseColor(SK_ColorWHITE);
+    for (int y = firstBlackRow; y < lastBlackRow; ++y) {
+        for (int x = 0; x < kWidth; ++x) {
+            *bm.getAddr32(x, y) = SkPackARGB32(0xFF, 0x0, 0x0, 0x0);
+        }
+    }
+
+    bm.setAlphaType(SkAlphaType::kOpaque_SkAlphaType);
+    bm.setImmutable();
+
+    return SkImage::MakeFromBitmap(bm);
+}
+
+// GM to reproduce crbug.com/673261.
+class FilterBugGM : public skiagm::GM {
+public:
+    FilterBugGM() { this->setBGColor(SK_ColorRED); }
+
+protected:
+    SkString onShortName() override { return SkString("filterbug"); }
+
+    SkISize onISize() override { return SkISize::Make(150, 150); }
+
+    void onOnceBeforeDraw() override {
+        // The top texture has 5 black rows on top and then 22 white rows on the bottom
+        fTop = make_image(0, 5);
+        // The bottom texture has 5 black rows on the bottom and then 22 white rows on the top
+        fBot = make_image(22, 27);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        static const SkFilterQuality kFilterQuality = SkFilterQuality::kHigh_SkFilterQuality;
+        static const bool kDoAA = true;
+
+        {
+            SkRect r1 = SkRect::MakeXYWH(50.0f, 0.0f, 50.0f, 50.0f);
+            SkPaint p1;
+            p1.setAntiAlias(kDoAA);
+            p1.setFilterQuality(kFilterQuality);
+            SkMatrix localMat;
+            localMat.setScaleTranslate(2.0f, 2.0f, 50.0f, 0.0f);
+            p1.setShader(SkImageShader::Make(fTop,
+                                             SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode,
+                                             &localMat));
+
+            canvas->drawRect(r1, p1);
+        }
+
+        {
+            SkRect r2 = SkRect::MakeXYWH(50.0f, 50.0f, 50.0f, 36.0f);
+
+            SkPaint p2;
+            p2.setColor(SK_ColorWHITE);
+            p2.setAntiAlias(kDoAA);
+            p2.setFilterQuality(kFilterQuality);
+
+            canvas->drawRect(r2, p2);
+        }
+
+        {
+            SkRect r3 = SkRect::MakeXYWH(50.0f, 86.0f, 50.0f, 50.0f);
+
+            SkPaint p3;
+            p3.setAntiAlias(kDoAA);
+            p3.setFilterQuality(kFilterQuality);
+            SkMatrix localMat;
+            localMat.setScaleTranslate(2.0f, 2.0f, 50.0f, 86.0f);
+            p3.setShader(SkImageShader::Make(fBot,
+                                             SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode,
+                                             &localMat));
+
+            canvas->drawRect(r3, p3);
+        }
+    }
+
+private:
+    sk_sp<SkImage> fTop;
+    sk_sp<SkImage> fBot;
+
+    typedef skiagm::GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM(return new FilterBugGM;)

gn/gm.gni

@@ -118,6 +118,7 @@ gm_sources = [
   "$_gm/filltypes.cpp",
   "$_gm/filltypespersp.cpp",
   "$_gm/filterbitmap.cpp",
+  "$_gm/filterbug.cpp",
   "$_gm/filterfastbounds.cpp",
   "$_gm/filterindiabox.cpp",
   "$_gm/fontcache.cpp",