Add a non-blocking "OneShotEvent" class

extensions/common/one_shot_event_unittest.cc

+// Copyright 2013 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.
+
+#include "extensions/common/one_shot_event.h"
+
+#include "base/bind.h"
+#include "base/run_loop.h"
+#include "base/test/test_simple_task_runner.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace extensions {
+
+namespace {
+
+void Increment(int* i) { ++*i; }

[not at google - send to devlin, 2013/05/16 22:26:11]

There are a couple more scenarios it would be nice to test:
- that is_signalled returns true from the callbacks
- that adding a another callback from a callback calls that another-callback
(would be good to test this with a couple chained together, and transitively,
but might be overkill)

[Jeffrey Yasskin, 2013/05/16 22:45:51]

Done.

+
+TEST(OneShotEventTest, RecordsSignal) {
+  OneShotEvent event;
+  EXPECT_FALSE(event.is_signaled());
+  event.Signal();
+  EXPECT_TRUE(event.is_signaled());
+}
+
+TEST(OneShotEventTest, CallsQueue) {
+  OneShotEvent event;
+  scoped_refptr<base::TestSimpleTaskRunner> runner(
+      new base::TestSimpleTaskRunner);
+  int i = 0;
+  event.Post(FROM_HERE, base::Bind(&Increment, &i), runner);
+  event.Post(FROM_HERE, base::Bind(&Increment, &i), runner);
+  EXPECT_EQ(0U, runner->GetPendingTasks().size());
+  event.Signal();
+  ASSERT_EQ(2U, runner->GetPendingTasks().size());
+  EXPECT_NE(runner->GetPendingTasks()[0].location.line_number(),
+            runner->GetPendingTasks()[1].location.line_number())
+      << "Make sure FROM_HERE is propagated.";
+  EXPECT_EQ(0, i);
+  runner->RunPendingTasks();
+  EXPECT_EQ(2, i);
+}
+
+TEST(OneShotEventTest, CallsAfterSignalDontRunInline) {
+  OneShotEvent event;
+  scoped_refptr<base::TestSimpleTaskRunner> runner(
+      new base::TestSimpleTaskRunner);
+  int i = 0;
+
+  event.Signal();
+  event.Post(FROM_HERE, base::Bind(&Increment, &i), runner);
+  EXPECT_EQ(1U, runner->GetPendingTasks().size());
+  EXPECT_EQ(0, i);
+  runner->RunPendingTasks();
+  EXPECT_EQ(1, i);
+}
+
+TEST(OneShotEventTest, PostDefaultsToCurrentMessageLoop) {
+  OneShotEvent event;
+  scoped_refptr<base::TestSimpleTaskRunner> runner(
+      new base::TestSimpleTaskRunner);
+  MessageLoop loop;
+  int runner_i = 0;
+  int loop_i = 0;
+
+  event.Post(FROM_HERE, base::Bind(&Increment, &runner_i), runner);
+  event.Post(FROM_HERE, base::Bind(&Increment, &loop_i));
+  event.Signal();
+  EXPECT_EQ(1U, runner->GetPendingTasks().size());
+  EXPECT_EQ(0, runner_i);
+  runner->RunPendingTasks();
+  EXPECT_EQ(1, runner_i);
+  EXPECT_EQ(0, loop_i);
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, loop_i);
+}
+
+}  // namespace
+}  // namespace extensions