Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks.

base/threading/sequenced_task_runner_handle_unittest.cc

Index: base/threading/sequenced_task_runner_handle_unittest.cc
diff --git a/base/threading/sequenced_task_runner_handle_unittest.cc b/base/threading/sequenced_task_runner_handle_unittest.cc
index 1080262f32f1a8617f4fa2da7de3f0aa1f2d76fd..6b8ecfe2a24dad6dc6f3c4e31ea53dcd82d258a5 100644
--- a/base/threading/sequenced_task_runner_handle_unittest.cc
+++ b/base/threading/sequenced_task_runner_handle_unittest.cc
@@ -24,12 +24,13 @@ namespace {
 class SequencedTaskRunnerHandleTest : public ::testing::Test {
  protected:
   static void GetTaskRunner(const Closure& callback) {

[gab, 2015/11/10 19:54:18]

A "Get" method that returns void feels weird to me.

[Bernhard Bauer, 2015/11/10 20:31:47]

Done.

-    // Use SequenceCheckerImpl to make sure it's not a no-op in Release builds.
-    scoped_ptr<SequenceCheckerImpl> sequence_checker(new SequenceCheckerImpl);
     ASSERT_TRUE(SequencedTaskRunnerHandle::IsSet());
     scoped_refptr<SequencedTaskRunner> task_runner =
         SequencedTaskRunnerHandle::Get();
     ASSERT_TRUE(task_runner);
+
+    // Use SequenceCheckerImpl to make sure it's not a no-op in Release builds.
+    scoped_ptr<SequenceCheckerImpl> sequence_checker(new SequenceCheckerImpl);
     task_runner->PostTask(
         FROM_HERE, base::Bind(&SequencedTaskRunnerHandleTest::CheckValidThread,
                               base::Passed(&sequence_checker), callback));
@@ -51,7 +52,7 @@ TEST_F(SequencedTaskRunnerHandleTest, FromMessageLoop) {
   run_loop.Run();
 }
 
-TEST_F(SequencedTaskRunnerHandleTest, FromSequencedWorkerPool) {
+TEST_F(SequencedTaskRunnerHandleTest, FromSequencedWorkerPoolTask) {
   // Wrap the SequencedWorkerPool to avoid leaks due to its asynchronous
   // destruction.
   SequencedWorkerPoolOwner owner(3, "Test");
@@ -64,6 +65,19 @@ TEST_F(SequencedTaskRunnerHandleTest, FromSequencedWorkerPool) {
   owner.pool()->Shutdown();
 }
 
+TEST_F(SequencedTaskRunnerHandleTest, FromUnsequencedTask) {

[gab, 2015/11/10 19:54:18]

Did you confirm that this test failed prior to the product side changes of this
CL?

[Bernhard Bauer, 2015/11/10 20:31:47]

Yes: 

[ RUN      ] SequencedTaskRunnerHandleTest.FromUnsequencedTask
../../base/threading/sequenced_task_runner_handle_unittest.cc:27: Failure
Value of: SequencedTaskRunnerHandle::IsSet()
  Actual: false
Expected: true
(It hangs after that, because I was too lazy to add something that would call
the callback in case of failure... 😃)

+  // Wrap the SequencedWorkerPool to avoid leaks due to its asynchronous
+  // destruction.
+  SequencedWorkerPoolOwner owner(3, "Test");
+  WaitableEvent event(false, false);
+  owner.pool()->PostWorkerTask(
+      FROM_HERE,
+      base::Bind(&SequencedTaskRunnerHandleTest::GetTaskRunner,
+                 base::Bind(&WaitableEvent::Signal, base::Unretained(&event))));
+  event.Wait();
+  owner.pool()->Shutdown();
+}
+
 class ThreadRunner : public DelegateSimpleThread::Delegate {
  public:
   void Run() override {