Update from https://crrev.com/327068

base/test/sequenced_worker_pool_owner.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/test/sequenced_worker_pool_owner.h"
 
 #include "base/location.h"
 #include "base/message_loop/message_loop.h"
 
 namespace base {
@@ skipping 25 matching lines @@
 }
 
 void SequencedWorkerPoolOwner::OnHasWork() {
   AutoLock lock(has_work_lock_);
   ++has_work_call_count_;
 }
 
 void SequencedWorkerPoolOwner::WillWaitForShutdown() {
   if (!will_wait_for_shutdown_callback_.is_null()) {
     will_wait_for_shutdown_callback_.Run();
+
+    // Release the reference to the callback to prevent retain cycles.
+    will_wait_for_shutdown_callback_ = Closure();
   }
 }
 
 void SequencedWorkerPoolOwner::OnDestruct() {
   constructor_message_loop_->PostTask(
       FROM_HERE,
       constructor_message_loop_->QuitWhenIdleClosure());
 }
 
 }  // namespace base