Implementation of PostTaskAndReply() in MessageLoopProxy and BrowserThread.

base/message_loop_proxy.cc

 // Copyright (c) 2010 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/message_loop_proxy.h"
 
+#include "base/bind.h"
+
 namespace base {
 
 MessageLoopProxy::MessageLoopProxy() {
 }
 
 MessageLoopProxy::~MessageLoopProxy() {
 }
 
+bool MessageLoopProxy::PostTaskAndReply(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    const Closure& reply) {
+  internal::PostTaskAndReplyRelay* relay =
+      new internal::PostTaskAndReplyRelay(from_here, task, reply);
+  if (!PostTask(from_here, base::Bind(&internal::PostTaskAndReplyRelay::Run,
+                                          base::Unretained(relay)))) {

[darin (slow to review), 2011/08/17 17:20:39]

nit: indent by 4 fewer characters?  since this is the second argument of the
base::Bind function call, i'd expect the arguments to be left-aligned in the
same column.  the current indenting makes it look like a continuation of the
first argument or something.

nit: no need for base:: prefix.

[awong, 2011/08/17 18:46:46]

Done.

+    delete relay;
+    return false;
+  }
+
+  return true;
+}
+
 void MessageLoopProxy::OnDestruct() const {
   delete this;
 }
 
+namespace internal {
+
+PostTaskAndReplyRelay::PostTaskAndReplyRelay(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    const Closure& reply)
+    : from_here_(from_here),
+      origin_loop_(MessageLoopProxy::current()) {
+  task_ = task;
+  reply_ = reply;
+}
+
+PostTaskAndReplyRelay::~PostTaskAndReplyRelay() {
+  DCHECK(origin_loop_->BelongsToCurrentThread());
+  task_.Reset();
+  reply_.Reset();
+}
+
+void PostTaskAndReplyRelay::Run() {
+  task_.Run();
+  origin_loop_->PostTask(
+      from_here_,

[darin (slow to review), 2011/08/17 17:20:39]

this could make the data in about:objects look confusing.  maybe we should
somehow append a suffix to from_here_ so that it will be identified as a the
reply task?

[awong, 2011/08/17 18:46:46]

Do you think so?  As is, the "FROM_HERE" is going to be from a PostTaskAndReply
call, which should be the point of interest right?

+      Bind(&PostTaskAndReplyRelay::RunReplyAndSelfDestruct,
+           base::Unretained(this)));
+}
+
+void PostTaskAndReplyRelay::RunReplyAndSelfDestruct() {
+  DCHECK(origin_loop_->BelongsToCurrentThread());
+  task_.Reset();

[darin (slow to review), 2011/08/17 17:20:39]

it seems like there might be some subtle, non-trivial reason for resetting this
task before invoking the reply callback.  maybe you should insert a comment here
explaining that reason?

[awong, 2011/08/17 18:46:46]

Done.

+
+  reply_.Run();
+
+  // Cue mission impossible theme.
+  delete this;
+}
+
+}  // namespace internal
+
 }  // namespace base