For unit tests, track additions to AtExitManager and warn.

base/at_exit.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_AT_EXIT_H_
 #define BASE_AT_EXIT_H_
 #pragma once
 
 #include <stack>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/synchronization/lock.h"
 
 namespace base {
 
+class TestWatchAtExitManager;
+
 // This class provides a facility similar to the CRT atexit(), except that
 // we control when the callbacks are executed. Under Windows for a DLL they
 // happen at a really bad time and under the loader lock. This facility is
 // mostly used by base::Singleton.
 //
 // The usage is simple. Early in the main() or WinMain() scope create an
 // AtExitManager object on the stack:
 // int main(...) {
 //    base::AtExitManager exit_manager;
 //
@@ skipping 23 matching lines @@
   static void ProcessCallbacksNow();
 
  protected:
   // This constructor will allow this instance of AtExitManager to be created
   // even if one already exists.  This should only be used for testing!
   // AtExitManagers are kept on a global stack, and it will be removed during
   // destruction.  This allows you to shadow another AtExitManager.
   explicit AtExitManager(bool shadow);
 
  private:
+  friend class TestWatchAtExitManager;
+
   base::Lock lock_;
   std::stack<base::Closure> stack_;
   AtExitManager* next_manager_;  // Stack of managers to allow shadowing.
 
   DISALLOW_COPY_AND_ASSIGN(AtExitManager);
 };
 
 #if defined(UNIT_TEST)
 class ShadowingAtExitManager : public AtExitManager {
  public:
   ShadowingAtExitManager() : AtExitManager(true) {}
 };
 #endif  // defined(UNIT_TEST)
 
 }  // namespace base
 
 #endif  // BASE_AT_EXIT_H_