Clear PostTaskAndReply task on the destination thread (3)

base/threading/post_task_and_reply_impl.cc

Index: base/threading/post_task_and_reply_impl.cc
diff --git a/base/threading/post_task_and_reply_impl.cc b/base/threading/post_task_and_reply_impl.cc
index 7899f65f94bd792e3f9bd2f277a9e11595e590b7..9600369540e37a59875192b6d78c8ea7d12cc919 100644
--- a/base/threading/post_task_and_reply_impl.cc
+++ b/base/threading/post_task_and_reply_impl.cc
@@ -28,22 +28,21 @@ namespace {
 class PostTaskAndReplyRelay {
  public:
   PostTaskAndReplyRelay(const tracked_objects::Location& from_here,
-                        const Closure& task,

[gab, 2017/01/31 19:34:59]

Can this CL be focused on this change only? (i.e. move the mechanical renames
and uncontroversial std::move changes to a precursor CL?)

[tzik, 2017/02/07 08:05:35]

Sure. Let me split them to a separate CL.

-                        const Closure& reply)
+                        Closure task,
+                        Closure reply)
       : sequence_checker_(),
         from_here_(from_here),
         origin_task_runner_(SequencedTaskRunnerHandle::Get()),
-        reply_(reply),
-        task_(task) {}
+        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)));
@@ -53,10 +52,10 @@ class PostTaskAndReplyRelay {
   void RunReplyAndSelfDestruct() {
     DCHECK(sequence_checker_.CalledOnValidSequence());
 
-    // Force |task_| to be released before |reply_| is to ensure that no one
+    // Ensure |task_| to be released before |reply_| is to ensure that no one

[dcheng, 2017/02/07 07:28:44]

Nit: reword to fix some minor typos in the rest of this comment

// 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.

[tzik, 2017/02/07 08:05:34]

Acknowledged.

[tzik, 2017/02/07 08:33:26]

Done.

     // accidentally depends on |task_| keeping one of its arguments alive while
     // |reply_| is executing.
-    task_.Reset();
+    DCHECK(!task_);
 
     reply_.Run();
 
@@ -77,12 +76,12 @@ namespace internal {
 
 bool PostTaskAndReplyImpl::PostTaskAndReply(
     const tracked_objects::Location& from_here,
-    const Closure& task,
-    const Closure& reply) {
+    Closure task,
+    Closure reply) {
   DCHECK(!task.is_null()) << from_here.ToString();
   DCHECK(!reply.is_null()) << from_here.ToString();
   PostTaskAndReplyRelay* relay =
-      new PostTaskAndReplyRelay(from_here, task, reply);
+      new PostTaskAndReplyRelay(from_here, std::move(task), std::move(reply));
   // PostTaskAndReplyRelay self-destructs after executing |reply|. On the flip
   // side though, it is intentionally leaked if the |task| doesn't complete
   // before the origin sequence stops executing tasks. Annotate |relay| as leaky