Mojo: Don't do any work in ProxyMessagePipeEndpoint's destructor.

mojo/system/proxy_message_pipe_endpoint.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 "mojo/system/proxy_message_pipe_endpoint.h"
 
 #include <string.h>
 
 #include "base/logging.h"
 #include "mojo/system/channel_endpoint.h"
 #include "mojo/system/local_message_pipe_endpoint.h"
 #include "mojo/system/message_pipe_dispatcher.h"
 
 namespace mojo {
 namespace system {
 
 ProxyMessagePipeEndpoint::ProxyMessagePipeEndpoint(
     ChannelEndpoint* channel_endpoint)
     : channel_endpoint_(channel_endpoint) {
 }
 
 ProxyMessagePipeEndpoint::~ProxyMessagePipeEndpoint() {
-  channel_endpoint_->DetachFromMessagePipe();
+  DCHECK(!channel_endpoint_.get());
 }
 
 MessagePipeEndpoint::Type ProxyMessagePipeEndpoint::GetType() const {
   return kTypeProxy;
 }
 
 bool ProxyMessagePipeEndpoint::OnPeerClose() {
+  DetachIfNecessary();
   return false;
 }
 
 // Note: We may have to enqueue messages even when our (local) peer isn't open
 // -- it may have been written to and closed immediately, before we were ready.
 // This case is handled in |Run()| (which will call us).
 void ProxyMessagePipeEndpoint::EnqueueMessage(
     scoped_ptr<MessageInTransit> message) {
   DCHECK(channel_endpoint_.get());
   LOG_IF(WARNING, !channel_endpoint_->EnqueueMessage(message.Pass()))
       << "Failed to write enqueue message to channel";
 }
 
+void ProxyMessagePipeEndpoint::Close() {
+  DetachIfNecessary();
+}
+
+void ProxyMessagePipeEndpoint::DetachIfNecessary() {
+  if (channel_endpoint_.get()) {
+    channel_endpoint_->DetachFromMessagePipe();
+    channel_endpoint_ = nullptr;
+  }
+}
+
 }  // namespace system
 }  // namespace mojo