Register SimpleTaskExecutors for Blink threads

This is needed for implementing PostTaskHere and base::CurrentThread traits.

Bug: 835323
Change-Id: I238f9edeb6097b3f8da64294a515a7f461c6ae5e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1833588
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702083}

third_party/blink/renderer/platform/scheduler/DEPS

@@ -40,6 +40,8 @@ include_rules = [
   "+base/task/sequence_manager/sequence_manager.h",
   "+base/task/sequence_manager/task_queue.h",
   "+base/task/sequence_manager/time_domain.h",
+  "+base/task/simple_task_executor.h",
+  "+base/task/task_executor.h",
   "+base/task/task_traits.h",
   "+base/threading/platform_thread.h",
   "+base/threading/sequenced_task_runner_handle.h",

third_party/blink/renderer/platform/scheduler/common/scheduler_helper.cc

@@ -40,6 +40,8 @@ void SchedulerHelper::InitDefaultQueues(
 
   DCHECK(sequence_manager_);
   sequence_manager_->SetDefaultTaskRunner(default_task_runner_);
+
+  simple_task_executor_.emplace(default_task_runner_);
 }
 
 SchedulerHelper::~SchedulerHelper() {

third_party/blink/renderer/platform/scheduler/common/scheduler_helper.h

@@ -10,6 +10,7 @@
 
 #include "base/macros.h"
 #include "base/task/sequence_manager/sequence_manager.h"
+#include "base/task/simple_task_executor.h"
 #include "base/time/tick_clock.h"
 #include "third_party/blink/public/platform/task_type.h"
 #include "third_party/blink/renderer/platform/platform_export.h"
@@ -134,6 +135,7 @@ class PLATFORM_EXPORT SchedulerHelper
   Observer* observer_;  // NOT OWNED
 
   UkmTaskSampler ukm_task_sampler_;
+  base::Optional<base::SimpleTaskExecutor> simple_task_executor_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerHelper);
 };

third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl_unittest.cc

@@ -16,6 +16,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/task/sequence_manager/test/fake_task.h"
 #include "base/task/sequence_manager/test/sequence_manager_for_test.h"
+#include "base/task/task_executor.h"
 #include "base/test/bind_test_util.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/scoped_feature_list.h"
@@ -45,6 +46,7 @@ namespace scheduler {
 namespace main_thread_scheduler_impl_unittest {
 
 using testing::Mock;
+using testing::NotNull;
 using InputEventState = WebThreadScheduler::InputEventState;
 using base::sequence_manager::FakeTask;
 using base::sequence_manager::FakeTaskTiming;
@@ -2106,6 +2108,22 @@ TEST_P(MainThreadSchedulerImplTest,
   EXPECT_FALSE(BlockingInputExpectedSoon());
 }
 
+TEST_P(MainThreadSchedulerImplTest,
+       GetTaskExecutorForCurrentThreadInPostedTask) {
+  base::TaskExecutor* task_executor = base::GetTaskExecutorForCurrentThread();
+  EXPECT_THAT(task_executor, NotNull());
+
+  base::RunLoop run_loop;
+
+  default_task_runner_->PostTask(
+      FROM_HERE, base::BindLambdaForTesting([&]() {
+        EXPECT_EQ(base::GetTaskExecutorForCurrentThread(), task_executor);
+        run_loop.Quit();
+      }));
+
+  run_loop.Run();
+}
+
 class MainThreadSchedulerImplWithMessageLoopTest
     : public MainThreadSchedulerImplTest {
  public:

third_party/blink/renderer/platform/scheduler/worker/worker_thread_unittest.cc

@@ -8,6 +8,7 @@
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/task/task_executor.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
@@ -161,6 +162,13 @@ TEST_F(WorkerThreadTest, TestShutdown) {
   thread_.reset();
 }
 
+TEST_F(WorkerThreadTest, GetTaskExecutorForCurrentThreadInPostedTask) {
+  RunOnWorkerThread(FROM_HERE, base::BindOnce([]() {
+                      EXPECT_THAT(base::GetTaskExecutorForCurrentThread(),
+                                  testing::NotNull());
+                    }));
+}
+
 }  // namespace worker_thread_unittest
 }  // namespace scheduler
 }  // namespace blink