Update from https://crrev.com/320931

base/threading/sequenced_worker_pool_unittest.cc

 // Copyright (c) 2012 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_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 130 matching lines @@
   // during destruction of the SequencedWorkerPool.
   void PostRepostingTask(
       const scoped_refptr<SequencedWorkerPool>& pool,
       const scoped_refptr<DestructionDeadlockChecker>& checker) {
     Closure reposting_task =
         base::Bind(&TestTracker::PostRepostingTask, this, pool, checker);
     pool->PostWorkerTaskWithShutdownBehavior(
         FROM_HERE, reposting_task, SequencedWorkerPool::SKIP_ON_SHUTDOWN);
   }
 
+  // This task reposts itself back onto the SequencedWorkerPool before it
+  // finishes running.
+  void PostRepostingBlockingTask(
+      const scoped_refptr<SequencedWorkerPool>& pool,
+      const SequencedWorkerPool::SequenceToken& token) {
+    Closure reposting_task =
+        base::Bind(&TestTracker::PostRepostingBlockingTask, this, pool, token);
+    pool->PostSequencedWorkerTaskWithShutdownBehavior(token,
+        FROM_HERE, reposting_task, SequencedWorkerPool::BLOCK_SHUTDOWN);
+  }
+
   // Waits until the given number of tasks have started executing.
   void WaitUntilTasksBlocked(size_t count) {
     {
       base::AutoLock lock(lock_);
       while (started_events_ < count)
         cond_var_.Wait();
     }
     cond_var_.Signal();
   }
 
@@ skipping 627 matching lines @@
     scoped_refptr<DestructionDeadlockChecker> checker(
         new DestructionDeadlockChecker(pool()));
     tracker()->PostRepostingTask(pool(), checker);
   }
 
   // Shutting down the pool should destroy the DestructionDeadlockCheckers,
   // which in turn should not deadlock in their destructors.
   pool()->Shutdown();
 }
 
+// Similar to the test AvoidsDeadlockOnShutdown, but there are now also
+// sequenced, blocking tasks in the queue during shutdown.
+TEST_F(SequencedWorkerPoolTest,
+       AvoidsDeadlockOnShutdownWithSequencedBlockingTasks) {
+  const std::string sequence_token_name("name");
+  for (int i = 0; i < 4; ++i) {
+    scoped_refptr<DestructionDeadlockChecker> checker(
+        new DestructionDeadlockChecker(pool()));
+    tracker()->PostRepostingTask(pool(), checker);
+
+    SequencedWorkerPool::SequenceToken token1 =
+        pool()->GetNamedSequenceToken(sequence_token_name);
+    tracker()->PostRepostingBlockingTask(pool(), token1);
+  }
+
+  // Shutting down the pool should destroy the DestructionDeadlockCheckers,
+  // which in turn should not deadlock in their destructors.
+  pool()->Shutdown();
+}
+
 // Verify that FlushForTesting works as intended.
 TEST_F(SequencedWorkerPoolTest, FlushForTesting) {
   // Should be fine to call on a new instance.
   pool()->FlushForTesting();
 
   // Queue up a bunch of work, including  a long delayed task and
   // a task that produces additional tasks as an artifact.
   pool()->PostDelayedWorkerTask(
       FROM_HERE,
       base::Bind(&TestTracker::FastTask, tracker(), 0),
@@ skipping 147 matching lines @@
     SequencedWorkerPoolSequencedTaskRunner, TaskRunnerTest,
     SequencedWorkerPoolSequencedTaskRunnerTestDelegate);
 
 INSTANTIATE_TYPED_TEST_CASE_P(
     SequencedWorkerPoolSequencedTaskRunner, SequencedTaskRunnerTest,
     SequencedWorkerPoolSequencedTaskRunnerTestDelegate);
 
 }  // namespace
 
 }  // namespace base