[Chromoting] Fix DCHECK when shutting down It2Me host from client side

remoting/host/it2me/it2me_host.cc

 // Copyright 2013 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 "remoting/host/it2me/it2me_host.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 84 matching lines @@
 
 void It2MeHost::Disconnect() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   host_context_->network_task_runner()->PostTask(
       FROM_HERE, base::Bind(&It2MeHost::Shutdown, this));
 }
 
 void It2MeHost::Shutdown() {
   DCHECK(host_context_->network_task_runner()->BelongsToCurrentThread());
 
+  // Shutdown is expected to be called twice, if OnClientDisconnected has been
+  // called. See http://crbug.com/617474 for details.

[Sergey Ulanov, 2016/06/08 21:54:04]

The link to the bug is not useful here. I would just remove the comment - the
code is self-explanatory.

[Hzj_jie, 2016/06/08 23:12:20]

I would prefer to keep it, since the condition of returning is a little bit
magic to me. i.e. One may need to search for the references of Shutdown function
to understand why the Shutdown function may be called twice in some scenarios.

[Sergey Ulanov, 2016/06/08 23:26:15]

Ok, then I suggest rewording:
 // Disconnect() may be called even when after the host been
 // already stopped. Ignore repeated calls.


Also it may be useful to rename Shutdown() to DisconnectOnNetworkThread().

+  if (state_ == kDisconnected) {
+    return;
+  }
+
   confirmation_dialog_proxy_.reset();
 
   host_event_logger_.reset();
   if (host_) {
     host_->RemoveStatusObserver(this);
     host_.reset();
   }
 
   register_request_.reset();
   host_status_logger_.reset();
@@ skipping 401 matching lines @@
   std::unique_ptr<It2MeConfirmationDialogFactory> confirmation_dialog_factory(
       new It2MeConfirmationDialogFactory());
   std::unique_ptr<PolicyWatcher> policy_watcher =
       PolicyWatcher::Create(policy_service_, context->file_task_runner());
   return new It2MeHost(std::move(context), std::move(policy_watcher),
                        std::move(confirmation_dialog_factory), observer,
                        xmpp_server_config, directory_bot_jid);
 }
 
 }  // namespace remoting