Fix flaky FileFlusherTest.DuplicateRequests

chrome/browser/chromeos/base/file_flusher.h

 // Copyright 2016 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 CHROME_BROWSER_CHROMEOS_BASE_FILE_FLUSHER_H_
 #define CHROME_BROWSER_CHROMEOS_BASE_FILE_FLUSHER_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 20 matching lines @@
                     const base::Closure& callback);
 
   // Set a callback for every file flush for test. Note the callback is
   // called on a blocking pool thread.
   using OnFlushCallback = base::Callback<void(const base::FilePath&)>;
   void set_on_flush_callback_for_test(
       const OnFlushCallback& on_flush_callback) {
     on_flush_callback_for_test_ = on_flush_callback;
   }
 
+  void PauseForTest();
+  void ResumeForTest();
+
  private:
   // Job for the flushing requests.
   class Job;
 
   // Starts the first job in |jobs_|.
   void ScheduleJob();
 
   // Invoked by a Job when it finishes.
   void OnJobDone(Job* job);
 
   // Not owned. Job manages its own life time.
   std::vector<Job*> jobs_;
 
   // A callback for testing to be invoked when a file is flushed.
   OnFlushCallback on_flush_callback_for_test_;
 
+  bool paused_for_test_ = false;
+
   base::WeakPtrFactory<FileFlusher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileFlusher);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_BASE_FILE_FLUSHER_H_