Add a bench to test SkTileImageFilter.

Tests in three modes: no tiling, 32x32 tiled rendering, and 64x64 tiled
rendering.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1559403003

Review URL: https://codereview.chromium.org/1559403003

bench/TileImageFilterBench.cpp

@@ -0,0 +1,73 @@
+/*
+ * 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
+
+// This bench exercises SkTileImageFilter drawn from a 50x50 source to
+// a 512x512 destination. It is drawn using a single rect, or "tiled"
+// rendering (using 32x32, 64x64 tiles). Tiled rendering is currently an order
+// of magnitude slower, since SkTileImageFilter does not clip the
+// source or destination rects.
+
+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();
+                        SkIRect clipIRect = SkIRect::MakeXYWH(x, y, fTileSize, fTileSize);
+                        canvas->clipRect(SkRect::Make(clipIRect));
+                        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);)