Implement a poor man's PostAfterStartupTask() function.

base/synchronization/cancellation_flag.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_CANCELLATION_FLAG_H_
 #define BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_
 
 #include "base/base_export.h"
 #include "base/atomicops.h"
 #include "base/threading/platform_thread.h"
@@ skipping 11 matching lines @@
 #if !defined(NDEBUG)
     set_on_ = PlatformThread::CurrentId();
 #endif
   }
   ~CancellationFlag() {}
 
   // Set the flag. May only be called on the thread which owns the object.
   void Set();
   bool IsSet() const;  // Returns true iff the flag was set.
 
+  // Intended to help with testing.
+  void UnsafeReset();

[jam, 2015/04/08 20:34:27]

nit: testing methods need to end with ForTesting() so that presubmit checks
catch if they're called by non-testing code

[michaeln, 2015/04/08 21:57:25]

Done.

+
  private:
   base::subtle::Atomic32 flag_;
 #if !defined(NDEBUG)
   PlatformThreadId set_on_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(CancellationFlag);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_