IPC: Fix attachment brokering race condition.

ipc/ipc_channel_common.cc

 // Copyright 2014 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 "build/build_config.h"
 #include "ipc/ipc_channel.h"
 
 namespace IPC {
 
 // static
@@ skipping 34 matching lines @@
   return Channel::Create(channel_handle, Channel::MODE_SERVER, listener);
 }
 
 Channel::~Channel() {
 }
 
 bool Channel::IsSendThreadSafe() const {
   return false;
 }
 
+void Channel::OnSetAttachmentBrokerEndpoint() {
+  CHECK(!did_start_connect_);
+}
+
+void Channel::WillConnect() {
+  did_start_connect_ = true;
+}
+
 }  // namespace IPC