Add a non-blocking "OneShotEvent" class

extensions/common/one_shot_event_unittest.cc

Index: extensions/common/one_shot_event_unittest.cc
diff --git a/extensions/common/one_shot_event_unittest.cc b/extensions/common/one_shot_event_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ec2ddfd0fec471df62e68efafba9ae7cc35c9a79
--- /dev/null
+++ b/extensions/common/one_shot_event_unittest.cc
@@ -0,0 +1,111 @@
+// 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; }
+
+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);
+}
+
+void CheckSignaledAndPostIncrement(
+    OneShotEvent* event,
+    const scoped_refptr<base::TaskRunner>& runner,
+    int* i) {
+  EXPECT_TRUE(event->is_signaled());
+  event->Post(FROM_HERE, base::Bind(&Increment, i), runner);
+}
+
+TEST(OneShotEventTest, IsSignaledAndPostsFromCallbackWork) {
+  OneShotEvent event;
+  scoped_refptr<base::TestSimpleTaskRunner> runner(
+      new base::TestSimpleTaskRunner);
+  int i = 0;
+
+  event.Post(FROM_HERE,
+             base::Bind(&CheckSignaledAndPostIncrement, &event, runner, &i),
+             runner);
+  EXPECT_EQ(0, i);
+  event.Signal();
+
+  // CheckSignaledAndPostIncrement is queued on |runner|.
+  EXPECT_EQ(1U, runner->GetPendingTasks().size());
+  EXPECT_EQ(0, i);
+  runner->RunPendingTasks();
+  // Increment is queued on |runner|.
+  EXPECT_EQ(1U, runner->GetPendingTasks().size());
+  EXPECT_EQ(0, i);
+  runner->RunPendingTasks();
+  // Increment has run.
+  EXPECT_EQ(0U, runner->GetPendingTasks().size());
+  EXPECT_EQ(1, i);
+}
+
+}  // namespace
+}  // namespace extensions