[NTP Snippets] Refactor background scheduling for remote suggestions

components/ntp_snippets/remote/remote_suggestions_scheduler.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 COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_H_
-#define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_H_
-
-#include "base/macros.h"
-#include "base/time/time.h"
-
-namespace ntp_snippets {
-
-// Class to take care of scheduling of periodic updates of snippets. There are
-// two types of scheduled updates:
-//  - "hard" ones that should outlive current running instance of Chrome. These
-//  should get triggered according to their schedule even if Chrome is not
-//  running at the given moment. This is OS-dependent, may be unavilable on
-//  some platforms.
-//  - "soft" ones that get triggered only if Chrome stays running until the
-//  scheduled point.
-class RemoteSuggestionsScheduler {
- public:
-  // Interface to perform the scheduled update.
-  class Updater {
-    virtual void HardUpdate();
-    virtual void SoftUpdate();
-  };
-
-  // The passed in |updater| is called when an update is due according to the
-  // schedule. Note that hard fetches get access to the |updater| via the keyed
-  // ContentSuggestionService because the concrete instance passed to
-  // RemoteSuggestionsScheduler when the hard fetch was scheduled may not exist
-  // any more when the hard update is due.
-  explicit RemoteSuggestionsScheduler(Updater* updater);
-
-  // Schedules both "soft" and "hard" fetches. First removes existing schedule
-  // before scheduling new updates.
-  void Schedule();
-
-  // Removes any existing schedule.
-  void Unschedule();
-
-  // Schedule periodic fetching of snippets, with different periods depending on
-  // network state. Once per period, the concrete implementation should call
-  // RemoteSuggestionsUpdater::HardUpdate where RemoteSuggestionsUpdater is
-  // obtained from ContentSuggestionsService.
-  // Any of the periods can be zero to indicate that the corresponding task
-  // should not be scheduled.
-  virtual bool Schedule(base::TimeDelta period_wifi,
-                        base::TimeDelta period_fallback) = 0;
-
-  // Cancel any scheduled tasks.
-  virtual bool Unschedule() = 0;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(RemoteSuggestionsHardScheduler);
-};
-
-}  // namespace ntp_snippets
-
-#endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_HARD_SCHEDULER_H_