[SyncFS] Refine SyncProcessRunner's throttling algorithm for parallel task support

chrome/browser/sync_file_system/sync_process_runner.h

 // Copyright 2013 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_SYNC_FILE_SYSTEM_SYNC_PROCESS_RUNNER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_PROCESS_RUNNER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 57 matching lines @@
                     Client* client,
                     scoped_ptr<TimerHelper> timer_helper,
                     int max_parallel_task);
   virtual ~SyncProcessRunner();
 
   // Subclass must implement this.
   virtual void StartSync(const SyncStatusCallback& callback) = 0;
 
   // Schedules a new sync.
   void Schedule();
-  void ScheduleIfNotRunning();
 
   int64 pending_changes() const { return pending_changes_; }
 
  protected:
   void OnChangesUpdated(int64 pending_changes);
   SyncFileSystemService* GetSyncService();
 
   // Returns the current service state.  Default implementation returns
   // sync_service()->GetSyncServiceState().
   virtual SyncServiceState GetServiceState();
 
  private:
-  void Finished(const base::TimeTicks& start_time, SyncStatusCode status);
+  void Finished(const base::TimeTicks& start_time,
+                SyncStatusCode status);
   void Run();
   void ScheduleInternal(int64 delay);
 
+  // Throttles new sync for |base_delay| milliseconds for an error case.
+  // If new sync is already throttled, back off the duration.
+  void ThrottleSync(int64 base_delay);
+
+  // Clears old throttling setting that is already over.
+  void ResetOldThrottling();
+  void ResetThrottling();
+
   std::string name_;
   Client* client_;
   int max_parallel_task_;
   int running_tasks_;
   scoped_ptr<TimerHelper> timer_helper_;
   base::TimeTicks last_scheduled_;
+
+  base::TimeTicks throttle_from_;
+  base::TimeTicks throttle_until_;
+
   int64 current_delay_;
   int64 last_delay_;
   int64 pending_changes_;
   base::WeakPtrFactory<SyncProcessRunner> factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncProcessRunner);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_PROCESS_RUNNER_H_