Enforce singleton not allowed behavior for CONTINUE_ON_SHUTDOWN tasks

net/proxy/dhcpcsvc_init_win.cc

 // Copyright (c) 2011 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 "net/proxy/dhcpcsvc_init_win.h"
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 
 #include <dhcpcsdk.h>
 #include <dhcpv6csdk.h>
 
 namespace {
 
 class DhcpcsvcInitSingleton {
  public:
   DhcpcsvcInitSingleton() {
     DWORD version = 0;
     DWORD err = DhcpCApiInitialize(&version);
     DCHECK(err == ERROR_SUCCESS);  // DCHECK_EQ complains of unsigned mismatch.
   }
-
-  ~DhcpcsvcInitSingleton() {

[gab, 2016/04/26 11:53:18]

Make the destructor private w/ a comment of why it should always be leaked.

[Patrick Monette, 2016/04/26 19:05:28]

The comment that explain that is Worker pool threads that use the DHCP API may
still be running. Leak instance  and skip cleanup.

Do you think it's not clean enough?

[Patrick Monette, 2016/04/26 19:18:38]

clear*

-    // Worker pool threads that use the DHCP API may still be running, so skip
-    // cleanup.
-  }
 };
 
-static base::LazyInstance<DhcpcsvcInitSingleton> g_dhcpcsvc_init_singleton =
-    LAZY_INSTANCE_INITIALIZER;
+// Worker pool threads that use the DHCP API may still be running. Leak instance

[robliao, 2016/04/25 23:05:25]

s/running/running at shutdown/

[Patrick Monette, 2016/04/26 19:05:27]

Done.

+// and skip cleanup.
+static base::LazyInstance<DhcpcsvcInitSingleton>::Leaky
+    g_dhcpcsvc_init_singleton = LAZY_INSTANCE_INITIALIZER;

[gab, 2016/04/26 11:53:18]

Is the change in this file required to land the other one? Feels unrelated to
CONTINUE_ON_SHUTDOWN?

[Patrick Monette, 2016/04/26 19:05:27]

Threads with CONTINUE_ON_SHUTDOWN behavior were accessing this singleton and the
DCHECK in sequenced_worker_pool was firing.

I could have made this change in a separate CL before the other one, but it is
such a small change and it gives context as to why I'm doing it.

[gab, 2016/04/26 20:11:47]

Ah I see, it wasn't obvious to me how the two were linked (hadn't realized
LazyInstance::Leaky had a special case skipping the AssertSingletonAllowed()
check :-)). Perhaps explain this in the CL description?

 
 }  // namespace
 
 namespace net {
 
 void EnsureDhcpcsvcInit() {
   g_dhcpcsvc_init_singleton.Get();
 }
 
 }  // namespace net