Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks."

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"
@@ skipping 10 matching lines @@
 
 }  // 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::GetSequenceTokenForCurrentThread().IsValid());
+    DCHECK(!SequencedWorkerPool::GetSequencedTaskRunnerForCurrentThread());
     return handle->task_runner_;
   }
 
-  // If we are on a worker thread for a SequencedBlockingPool that is running a
-  // sequenced task, return a SequencedTaskRunner for it.
-  scoped_refptr<base::SequencedWorkerPool> pool =
-      SequencedWorkerPool::GetWorkerPoolForCurrentThread();
-  if (pool) {
-    SequencedWorkerPool::SequenceToken sequence_token =
-        SequencedWorkerPool::GetSequenceTokenForCurrentThread();
-    DCHECK(sequence_token.IsValid());
-    DCHECK(pool->IsRunningSequenceOnCurrentThread(sequence_token));
-    return pool->GetSequencedTaskRunner(sequence_token);
+  // 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::GetSequenceTokenForCurrentThread().IsValid() ||
+         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);
 }
 
 SequencedTaskRunnerHandle::~SequencedTaskRunnerHandle() {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
   DCHECK_EQ(lazy_tls_ptr.Pointer()->Get(), this);
   lazy_tls_ptr.Pointer()->Set(nullptr);
 }
 
 }  // namespace base