[mojo-edk] Shutdown a node's bootstrap parent channel outside its lock.

mojo/edk/system/node_controller.cc

 // Copyright 2016 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 "mojo/edk/system/node_controller.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 482 matching lines @@
       node_->AcceptMessage(std::move(messages.front()));
       messages.pop();
     }
   }
   AttemptShutdownIfRequested();
 }
 
 void NodeController::DropAllPeers() {
   DCHECK(io_task_runner_->RunsTasksOnCurrentThread());
 
+  std::vector<scoped_refptr<NodeChannel>> all_peers;
   {
     base::AutoLock lock(parent_lock_);
     if (bootstrap_parent_channel_) {
-      bootstrap_parent_channel_->ShutDown();
-      bootstrap_parent_channel_ = nullptr;
+      // |bootstrap_parent_channel_| isn't null'd here becuase we rely on its
+      // existence to determine whether or not this is the root node. Once
+      // bootstrap_parent_channel_->ShutDown() has been called,
+      // |bootstrap_parent_channel_| is essentially a dead object and it doesn't
+      // matter if it's deleted now or when |this| is deleted.
+      // Note: |bootstrap_parent_channel_| is only modified on the IO thread.
+      all_peers.push_back(bootstrap_parent_channel_);
     }
   }
 
-  std::vector<scoped_refptr<NodeChannel>> all_peers;
   {
     base::AutoLock lock(peers_lock_);
     for (const auto& peer : peers_)
       all_peers.push_back(peer.second);
     for (const auto& peer : pending_children_)
       all_peers.push_back(peer.second);
     peers_.clear();
     pending_children_.clear();
     pending_peer_messages_.clear();
   }
@@ skipping 453 matching lines @@
     shutdown_callback_.Reset();
   }
 
   DCHECK(!callback.is_null());
 
   callback.Run();
 }
 
 }  // namespace edk
 }  // namespace mojo