Make PlatformFileForTransit a class on Windows.

remoting/host/remoting_me2me_host.cc

 // Copyright (c) 2012 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.
 //
 // This file implements a standalone host process for Me2Me.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
@@ skipping 972 matching lines @@
   NOTREACHED();
 #endif  // !defined(OS_WIN)
 }
 
 #if defined(OS_WIN)
 void HostProcess::InitializePairingRegistry(
     IPC::PlatformFileForTransit privileged_key,
     IPC::PlatformFileForTransit unprivileged_key) {
   DCHECK(context_->network_task_runner()->BelongsToCurrentThread());
   // |privileged_key| can be nullptr but not |unprivileged_key|.
-  DCHECK(unprivileged_key);
+  DCHECK(unprivileged_key.IsValid());
   // |pairing_registry_| should only be initialized once.
   DCHECK(!pairing_registry_);
 
   HKEY privileged_hkey = reinterpret_cast<HKEY>(
       IPC::PlatformFileForTransitToPlatformFile(privileged_key));
   HKEY unprivileged_hkey = reinterpret_cast<HKEY>(
       IPC::PlatformFileForTransitToPlatformFile(unprivileged_key));
 
   scoped_ptr<PairingRegistryDelegateWin> delegate(
       new PairingRegistryDelegateWin());
@@ skipping 742 matching lines @@
       base::TimeDelta::FromSeconds(kShutdownTimeoutSeconds));
   new HostProcess(std::move(context), &exit_code, &shutdown_watchdog);
 
   // Run the main (also UI) message loop until the host no longer needs it.
   message_loop.Run();
 
   return exit_code;
 }
 
 }  // namespace remoting