Revert of Add SyncScheduler for scheduling CryptAuth enrollments and syncing devices.

components/proximity_auth/cryptauth/sync_scheduler.h

-// Copyright 2015 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 COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_SYNC_SCHEDULER_H
-#define COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_SYNC_SCHEDULER_H
-
-#include "base/memory/weak_ptr.h"
-#include "base/time/time.h"
-
-namespace proximity_auth {
-
-// Interface for scheduling the next CryptAuth sync (e.g. enrollment or device
-// sync). The scheduler has two different strategies affecting when to perform
-// the next operation:
-//     PERIODIC_REFRESH: The last sync was made successfully, so we can wait a
-//         relatively long time before making another sync.
-//     AGGRESSIVE_RECOVERY: The last sync failed, so we try more aggressively to
-//         make enrollment attempts with subsequent backoff for repeated
-//         failures.
-// A random jitter is applied to each sync period to smooth qps to the server.
-class SyncScheduler {
- public:
-  // The sync strategies mentioned in the class comments.
-  enum class Strategy { PERIODIC_REFRESH, AGGRESSIVE_RECOVERY };
-
-  // The states that the scheduler can be in.
-  enum class SyncState { NOT_STARTED, WAITING_FOR_REFRESH, SYNC_IN_PROGRESS };
-
-  // An instance is passed to the delegate when the scheduler fires for each
-  // sync attempt. The delegate should call |Complete()| when the sync succeeds
-  // or fails to resume the scheduler.
-  class SyncRequest {
-   public:
-    explicit SyncRequest(base::WeakPtr<SyncScheduler> sync_scheduler);
-    ~SyncRequest();
-
-    void OnDidComplete(bool success);
-
-   protected:
-    // The parent scheduler that dispatched this request.
-    base::WeakPtr<SyncScheduler> sync_scheduler_;
-
-    // True if |OnDidComplete()| has been called.
-    bool completed_;
-
-    DISALLOW_COPY_AND_ASSIGN(SyncRequest);
-  };
-
-  // Handles the actual sync operation.
-  class Delegate {
-   public:
-    virtual ~Delegate() {}
-
-    // Called when the scheduler fires and requests a sync attempt. The delegate
-    // should call sync_request->Complete() when the request finishes.
-    virtual void OnSyncRequested(scoped_ptr<SyncRequest> sync_request) = 0;
-  };
-
-  virtual ~SyncScheduler() {}
-
-  // Starts the scheduler with an aggressive recovery strategy if
-  // |strategy| is true; otherwise, it will be started with
-  // periodic refresh.
-  //
-  // |elapsed_time_since_last_sync| is the time since the last successful sync,
-  // so we can determine the duration of the first sync period. For example, the
-  // scheduler will immediately issue a sync request if the elapsed time is
-  // greater than the refresh period.
-  virtual void Start(const base::TimeDelta& elapsed_time_since_last_sync,
-                     Strategy strategy) = 0;
-
-  // Cancels the current scheduled sync, and forces a sync immediately. Note
-  // that if this sync fails, the scheduler will adopt the AGGRESSIVE_RECOVERY
-  // strategy.
-  virtual void ForceSync() = 0;
-
-  // Returns the time until the next scheduled sync operation. If no sync is
-  // scheduled, a TimeDelta of zero will be returned.
-  virtual base::TimeDelta GetTimeToNextSync() const = 0;
-
-  // Returns the current sync strategy.
-  virtual Strategy GetStrategy() const = 0;
-
-  // Returns the current state of the scheduler.
-  virtual SyncState GetSyncState() const = 0;
-
- protected:
-  // Called by SyncRequest instances when the sync completes.
-  virtual void OnSyncCompleted(bool success) = 0;
-};
-
-}  // namespace proximity_auth
-
-#endif  // COMPONENTS_PROXIMITY_CRYPTAUTH_SYNC_SCHEDULER_H