Add a startup benchmark and rudimentary scripts for running benchmarks.

benchmarks/startup/BUILD.gn

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+group("startup") {
+  testonly = true
+
+  deps = [
+    ":app",
+    ":noop",
+  ]
+}
+
+shared_library("app") {
+  output_name = "mojo_benchmark_startup"
+  testonly = true
+
+  sources = [ "startup.cc" ]
+
+  deps = [
+    "//mojo/public/c/system:for_shared_library",
+  ]
+}
+
+executable("noop") {
+  output_name = "mojo_benchmark_startup_noop"
+  testonly = true
+
+  sources = [ "noop.cc" ]
+}