Add a perf test for async wait and fix a bug in mojo::RunLoop.

mojo/public/c/environment/tests/async_waiter_perftest_helpers.h

+// Copyright 2016 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.
+
+#ifndef MOJO_PUBLIC_C_ENVIRONMENT_TESTS_ASYNC_WAITER_PERFTEST_HELPERS_H_
+#define MOJO_PUBLIC_C_ENVIRONMENT_TESTS_ASYNC_WAITER_PERFTEST_HELPERS_H_
+
+#include <stdint.h>
+
+#include <functional>
+
+#include "mojo/public/c/environment/async_waiter.h"
+
+namespace mojo {
+namespace test {
+
+// Basic single-threaded perf test helper for |MojoAsyncWaiter|. This will keep
+// |num_handles| active async waits and activate them one at a time (with each
+// callback triggering the next). This sets up the test (setting up the initial
+// set of async waits), calls |run_loop_function|, and once that is done cleans
+// up. It returns the number of async waits completed. |run_loop_function|
+// should typically run the message/run loop and quit after some fixed amount of
+// time (it should probably measure the actual amount of time spent running, and
+// the return value should probably be normalized with respect to that).
+uint64_t DoAsyncWaiterPerfTest(const MojoAsyncWaiter* async_waiter,
+                               uint32_t num_handles,
+                               std::function<void()> run_loop_function);
+
+}  // namespace test
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_C_ENVIRONMENT_TESTS_ASYNC_WAITER_PERFTEST_HELPERS_H_