Add first benchmark

Summary: Implement some very basic benchmarking infra. We need benchmarks in css-layout and I want to add something now so that others have the option to follow an example when implementing a benchmark.

Reviewed By: lucasr

Differential Revision: D3648889

fbshipit-source-id: 60b93c6e5ed027a37195a9a5d86e681e3e79a5b9

benchmarks/CSSBenchmark.c

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#include "CSSBenchmark.h"
+
+#include <CSSLayout/CSSLayout.h>
+
+CSS_BENCHMARKS({
+
+  CSS_BENCHMARK("Stack with flex", {
+    CSSNodeRef root = CSSNodeNew();
+    CSSNodeStyleSetWidth(root, 100);
+    CSSNodeStyleSetHeight(root, 100);
+
+    for (int i = 0; i < 3; i++) {
+      CSSNodeRef child = CSSNodeNew();
+      CSSNodeStyleSetHeight(child, 20);
+      CSSNodeStyleSetFlex(child, 1);
+      CSSNodeInsertChild(root, child, 0);
+    }
+
+    CSSNodeCalculateLayout(root, 100, 100, CSSDirectionLTR);
+  });
+
+});