Clear PostTaskAndReply task on the destination thread (3)

base/threading/post_task_and_reply_impl.cc

 // Copyright (c) 2011 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/post_task_and_reply_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 21 matching lines @@
                         Closure task,
                         Closure reply)
       : sequence_checker_(),
         from_here_(from_here),
         origin_task_runner_(SequencedTaskRunnerHandle::Get()),
         reply_(std::move(reply)),
         task_(std::move(task)) {}
 
   ~PostTaskAndReplyRelay() {
     DCHECK(sequence_checker_.CalledOnValidSequence());
-    task_.Reset();
-    reply_.Reset();
   }
 
   void RunTaskAndPostReply() {
     task_.Run();
+    task_.Reset();
     origin_task_runner_->PostTask(
         from_here_, Bind(&PostTaskAndReplyRelay::RunReplyAndSelfDestruct,
                          base::Unretained(this)));
   }
 
  private:
   void RunReplyAndSelfDestruct() {
     DCHECK(sequence_checker_.CalledOnValidSequence());
 
-    // Force |task_| to be released before |reply_| is to ensure that no one
-    // accidentally depends on |task_| keeping one of its arguments alive while
-    // |reply_| is executing.
-    task_.Reset();
+    // Ensure |task_| has already been released before |reply_| to ensure that
+    // no one accidentally depends on |task_| keeping one of its arguments alive
+    // while |reply_| is executing.
+    DCHECK(!task_);
 
     reply_.Run();
 
     // Cue mission impossible theme.
     delete this;
   }
 
   const SequenceChecker sequence_checker_;
   const tracked_objects::Location from_here_;
   const scoped_refptr<SequencedTaskRunner> origin_task_runner_;
@@ skipping 24 matching lines @@
     delete relay;
     return false;
   }
 
   return true;
 }
 
 }  // namespace internal
 
 }  // namespace base