Add a simple microbenchmark framework, packaging, and sample tests.

src/platform/microbenchmark/benchmarks/getpid.cc

+// Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+// Some portions Copyright (c) 2009 The Chromium Authors.
+//
+// Microbenchmark of getpid()
+#include "microbenchmark/microbenchmark.h"
+
+#include <syscall.h>
+namespace chromeos {
+namespace benchmarks {
+
+static void GetPid(bool scaffold_only) {
+  if (!scaffold_only) syscall(__NR_getpid);
+}
+CHROMEOS_MICROBENCHMARK(GetPid, 1000000);
+
+}  // namespace benchmarks
+}  // namespace chromeos