Enable multiprocess by default on desktop mojo_runner.

mojo/message_pump/handle_watcher.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/message_pump/handle_watcher.h"
 
 #include <map>
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
@@ skipping 204 matching lines @@
   Requests requests_;
 
   DISALLOW_COPY_AND_ASSIGN(WatcherThreadManager);
 };
 
 WatcherThreadManager::~WatcherThreadManager() {
   thread_.Stop();
 }
 
 WatcherThreadManager* WatcherThreadManager::GetInstance() {
-  return base::Singleton<WatcherThreadManager>::get();
+  return base::Singleton<WatcherThreadManager,
+                         base::LeakySingletonTraits<WatcherThreadManager>>::

[jam, 2015/11/07 05:00:31]

we need to leak this because otherwise when the process dies, AtExitManager
waits for destruction which waits till the handle watcher thread is joined. but
that can't happen since the pump uses mojo message pipes to wake up the pump.
since mojo edk has been shutdown already, this never completes.

[sky, 2015/11/08 16:26:36]

Please add this comment to the code here.

[jam, 2015/11/09 18:20:58]

Done.

+      get();
 }
 
 WatcherID WatcherThreadManager::StartWatching(
     const Handle& handle,
     MojoHandleSignals handle_signals,
     base::TimeTicks deadline,
     const base::Callback<void(MojoResult)>& callback) {
   RequestData request_data;
   request_data.type = REQUEST_START;
   request_data.start_data.id = watcher_id_generator_.GetNext();
@@ skipping 230 matching lines @@
         this, handle, handle_signals, deadline, callback));
   }
 }
 
 void HandleWatcher::Stop() {
   state_.reset();
 }
 
 }  // namespace common
 }  // namespace mojo