Fix a possible mismatch in OS-specific code in WaitableEventWatcher.

base/synchronization/waitable_event_watcher.h

 // 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.
 
 #ifndef BASE_SYNCHRONIZATION_WAITABLE_EVENT_WATCHER_H_
 #define BASE_SYNCHRONIZATION_WAITABLE_EVENT_WATCHER_H_
 #pragma once
 
+#include "base/base_export.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include "base/win/object_watcher.h"
 #else
 #include "base/callback.h"
 #include "base/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #endif
 
-#include "base/base_export.h"
-
 namespace base {
 
 class Flag;
 class AsyncWaiter;
 class AsyncCallbackTask;
 class WaitableEvent;
 
 // -----------------------------------------------------------------------------
 // This class provides a way to wait on a WaitableEvent asynchronously.
 //
@@ skipping 24 matching lines @@
 // BEWARE: With automatically reset WaitableEvents, a signal may be lost if it
 // occurs just before a WaitableEventWatcher is deleted. There is currently no
 // safe way to stop watching an automatic reset WaitableEvent without possibly
 // missing a signal.
 //
 // NOTE: you /are/ allowed to delete the WaitableEvent while still waiting on
 // it with a Watcher. It will act as if the event was never signaled.
 // -----------------------------------------------------------------------------
 
 class BASE_EXPORT WaitableEventWatcher
-#if defined(OS_POSIX)
+#if !defined(OS_WIN)
     : public MessageLoop::DestructionObserver
 #endif
 {
  public:
 
   WaitableEventWatcher();
   virtual ~WaitableEventWatcher();
 
   class BASE_EXPORT Delegate {
    public:
@@ skipping 80 matching lines @@
 #endif
 
   WaitableEvent* event_;
 
   Delegate* delegate_;
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_WAITABLE_EVENT_WATCHER_H_