Add a bench to test SkTileImageFilter.

bench/TileImageFilterBench.cpp

Index: bench/TileImageFilterBench.cpp
diff --git a/bench/TileImageFilterBench.cpp b/bench/TileImageFilterBench.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..949baea6d716c9a7511377a095ad0ab7da799167
--- /dev/null
+++ b/bench/TileImageFilterBench.cpp
@@ -0,0 +1,67 @@
+/*
+ * 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 "Benchmark.h"
+#include "SkTileImageFilter.h"
+#include "SkCanvas.h"
+#include "SkPaint.h"
+#include "SkString.h"
+
+#define WIDTH 512
+#define HEIGHT 512
+
+

[robertphillips, 2016/01/05 20:45:48]

// This bench is interesting because ... ?

I'm assuming it exercises the optimization you added earlier, right?

[Stephen White, 2016/01/05 20:50:09]

Done.
It's actually for another optimization. But I haven't landed either one
yet.

+class TileImageFilterBench : public Benchmark {
+public:
+    TileImageFilterBench(int tileSize) : fTileSize(tileSize) {
+        if (tileSize > 0) {
+            fName.printf("tile_image_filter_tiled_%d", tileSize);
+        } else {
+            fName.printf("tile_image_filter");
+        }
+    }
+
+protected:
+    const char* onGetName() override {
+        return fName.c_str();
+    }
+
+    void onDraw(int loops, SkCanvas* canvas) override {
+        SkPaint paint;
+        SkAutoTUnref<SkImageFilter> tile(SkTileImageFilter::Create(
+            SkRect::MakeWH(50, 50),
+            SkRect::MakeWH(WIDTH, HEIGHT),
+            nullptr));
+        paint.setImageFilter(tile);
+
+        for (int i = 0; i < loops; i++) {
+            if (fTileSize > 0) {
+                for (int y = 0; y < HEIGHT; y += fTileSize) {
+                    for (int x = 0; x < WIDTH; x += fTileSize) {
+                        canvas->save();
+                        canvas->clipRect(SkRect::MakeXYWH(x, y, fTileSize, fTileSize));
+                        canvas->drawRect(SkRect::MakeWH(WIDTH, HEIGHT), paint);
+                        canvas->restore();
+                    }
+                }
+            } else {
+                canvas->drawRect(SkRect::MakeWH(WIDTH, HEIGHT), paint);
+            }
+        }
+    }
+
+private:
+    SkString fName;
+    // Note: this is the tile size used for tiled rendering, not for the size
+    // of the SkTileImageFilter source rect.
+    int fTileSize;
+    typedef Benchmark INHERITED;
+};
+
+DEF_BENCH(return new TileImageFilterBench(0);)
+DEF_BENCH(return new TileImageFilterBench(32);)
+DEF_BENCH(return new TileImageFilterBench(64);)