[base] Remove implicit-destination PostTask

No TaskTraits implcitly meant base::ThreadPool. The migration away
from this paradigm is complete (task APIs v3 is bringing explicit
API-as-destination). Remove this right away before we're ready to
completely remove post_task.h to avoid the addition of new callers
without an explicit destination.

Bug: 968047, 1026641
Change-Id: I54d04872498d340cfd8ec02aa88b3e9cba1a7547
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225541
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774758}

base/task/post_task.cc

@@ -62,19 +62,6 @@ TaskExecutor* GetTaskExecutorForTraits(const TaskTraits& traits) {
 
 }  // namespace
 
-bool PostTask(const Location& from_here, OnceClosure task) {
-  // TODO(skyostil): Make task traits required here too.
-  return PostDelayedTask(from_here, {ThreadPool()}, std::move(task),
-                         TimeDelta());
-}
-
-bool PostTaskAndReply(const Location& from_here,
-                      OnceClosure task,
-                      OnceClosure reply) {
-  return PostTaskAndReply(from_here, {ThreadPool()}, std::move(task),
-                          std::move(reply));
-}
-
 bool PostTask(const Location& from_here,
               const TaskTraits& traits,
               OnceClosure task) {

base/task/post_task.h

@@ -99,27 +99,6 @@ namespace base {
 // have to worry about this. You will encounter DCHECKs or nullptr dereferences
 // if this is violated. For tests, prefer base::test::TaskEnvironment.
 
-// Equivalent to calling PostTask with default TaskTraits.
-BASE_EXPORT bool PostTask(const Location& from_here, OnceClosure task);
-inline bool PostTask(OnceClosure task,
-                     const Location& from_here = Location::Current()) {
-  return PostTask(from_here, std::move(task));
-}
-
-// Equivalent to calling PostTaskAndReply with default TaskTraits.
-BASE_EXPORT bool PostTaskAndReply(const Location& from_here,
-                                  OnceClosure task,
-                                  OnceClosure reply);
-
-// Equivalent to calling PostTaskAndReplyWithResult with default TaskTraits.
-template <typename TaskReturnType, typename ReplyArgType>
-bool PostTaskAndReplyWithResult(const Location& from_here,
-                                OnceCallback<TaskReturnType()> task,
-                                OnceCallback<void(ReplyArgType)> reply) {
-  return PostTaskAndReplyWithResult(from_here, {ThreadPool()}, std::move(task),
-                                    std::move(reply));
-}
-
 // Posts |task| with specific |traits|. Returns false if the task definitely
 // won't run because of current shutdown state.
 BASE_EXPORT bool PostTask(const Location& from_here,

base/task/post_task_unittest.cc

@@ -99,10 +99,6 @@ class PostTaskTestWithExecutor : public ::testing::Test {
 };
 
 TEST_F(PostTaskTestWithExecutor, PostTaskToThreadPool) {
-  // Tasks without extension should not go to the TestTaskExecutor.
-  EXPECT_TRUE(PostTask(FROM_HERE, DoNothing()));
-  EXPECT_FALSE(executor_.runner()->HasPendingTask());
-
   EXPECT_TRUE(PostTask(FROM_HERE, {ThreadPool(), MayBlock()}, DoNothing()));
   EXPECT_FALSE(executor_.runner()->HasPendingTask());
 

base/threading/sequenced_task_runner_handle_unittest.cc

@@ -67,7 +67,7 @@ TEST_F(SequencedTaskRunnerHandleTest, FromThreadPoolSequencedTask) {
 }
 
 TEST_F(SequencedTaskRunnerHandleTest, NoHandleFromUnsequencedTask) {
-  base::PostTask(base::BindOnce(
+  base::ThreadPool::PostTask(base::BindOnce(
       []() { EXPECT_FALSE(SequencedTaskRunnerHandle::IsSet()); }));
   task_environment_.RunUntilIdle();
 }

content/public/test/browser_task_environment_unittest.cc

@@ -151,12 +151,12 @@ TEST(BrowserTaskEnvironmentTest, TraitsConstructor) {
   signaled_on_real_io_thread.TimedWait(base::TimeDelta::FromSeconds(5));
   EXPECT_TRUE(signaled_on_real_io_thread.IsSignaled());
 
-  // Tasks posted via PostTask don't run in ThreadPoolExecutionMode::QUEUED
-  // until RunUntilIdle is called.
+  // Tasks posted via ThreadPool::PostTask don't run in
+  // ThreadPoolExecutionMode::QUEUED until RunUntilIdle is called.
   base::AtomicFlag task_ran;
-  PostTask(FROM_HERE,
-           BindOnce([](base::AtomicFlag* task_ran) { task_ran->Set(); },
-                    Unretained(&task_ran)));
+  base::ThreadPool::PostTask(
+      FROM_HERE, BindOnce([](base::AtomicFlag* task_ran) { task_ran->Set(); },
+                          Unretained(&task_ran)));
 
   base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
   EXPECT_FALSE(task_ran.IsSet());