Add generic functions for getting typed variation parameter values

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_