An assert was being hit because WaitableEvent's dtor was calling CloseHandle ...

chrome/common/child_process_host.cc

 // Copyright (c) 2009 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 "chrome/common/child_process_host.h"
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/singleton.h"
@@ skipping 37 matching lines @@
   Singleton<ChildProcessList>::get()->push_back(this);
 }
 
 
 ChildProcessHost::~ChildProcessHost() {
   Singleton<ChildProcessList>::get()->remove(this);
 
   if (handle()) {
     watcher_.StopWatching();
     ProcessWatcher::EnsureProcessTerminated(handle());
+
+    // Above call took ownership, so don't want WaitableEvent to assert because
+    // the handle isn't valid anymore.
+    process_event_->Release();
   }
 }
 
 bool ChildProcessHost::CreateChannel() {
   channel_id_ = GenerateRandomChannelID(this);
   channel_.reset(new IPC::Channel(
       channel_id_, IPC::Channel::MODE_SERVER, &listener_));
   if (!channel_->Connect())
     return false;
 
@@ skipping 114 matching lines @@
 
     return *iterator_;
   } while (true);
 
   return NULL;
 }
 
 bool ChildProcessHost::Iterator::Done() {
   return iterator_ == Singleton<ChildProcessList>::get()->end();
 }