Introduce TaskRunnerHandle.

base/threading/sequenced_task_runner_handle.cc

 // Copyright 2015 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 "base/threading/sequenced_task_runner_handle.h"
 
 #include <utility>
 
-#include "base/lazy_instance.h"
-#include "base/logging.h"
-#include "base/threading/sequenced_worker_pool.h"
-#include "base/threading/thread_local.h"
-#include "base/threading/thread_task_runner_handle.h"
-
 namespace base {
 
-namespace {
-
-base::LazyInstance<base::ThreadLocalPointer<SequencedTaskRunnerHandle>>::Leaky
-    lazy_tls_ptr = LAZY_INSTANCE_INITIALIZER;
-
-}  // namespace
-
-// static
-scoped_refptr<SequencedTaskRunner> SequencedTaskRunnerHandle::Get() {
-  // Return the registered SequencedTaskRunner, if any.
-  const SequencedTaskRunnerHandle* handle = lazy_tls_ptr.Pointer()->Get();
-  if (handle) {
-    // Various modes of setting SequencedTaskRunnerHandle don't combine.
-    DCHECK(!base::ThreadTaskRunnerHandle::IsSet());
-    DCHECK(!SequencedWorkerPool::GetSequencedTaskRunnerForCurrentThread());
-    return handle->task_runner_;
-  }
-
-  // Return the SequencedTaskRunner obtained from SequencedWorkerPool, if any.
-  scoped_refptr<base::SequencedTaskRunner> task_runner =
-      SequencedWorkerPool::GetSequencedTaskRunnerForCurrentThread();
-  if (task_runner) {
-    DCHECK(!base::ThreadTaskRunnerHandle::IsSet());
-    return task_runner;
-  }
-
-  // Return the SingleThreadTaskRunner for the current thread otherwise.
-  return base::ThreadTaskRunnerHandle::Get();
-}
-
-// static
-bool SequencedTaskRunnerHandle::IsSet() {
-  return lazy_tls_ptr.Pointer()->Get() ||
-         SequencedWorkerPool::GetWorkerPoolForCurrentThread() ||
-         base::ThreadTaskRunnerHandle::IsSet();
-}
-
 SequencedTaskRunnerHandle::SequencedTaskRunnerHandle(
     scoped_refptr<SequencedTaskRunner> task_runner)
-    : task_runner_(std::move(task_runner)) {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-  DCHECK(!SequencedTaskRunnerHandle::IsSet());
-  lazy_tls_ptr.Pointer()->Set(this);
-}
+    : task_scope_(std::move(task_runner)) {}
 
-SequencedTaskRunnerHandle::~SequencedTaskRunnerHandle() {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-  DCHECK_EQ(lazy_tls_ptr.Pointer()->Get(), this);
-  lazy_tls_ptr.Pointer()->Set(nullptr);
-}
+SequencedTaskRunnerHandle::~SequencedTaskRunnerHandle() = default;
 
 }  // namespace base