[Remote suggestions] Report time distribution of triggers

components/ntp_snippets/remote/remote_suggestions_scheduler_impl.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_IMPL_H_
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_IMPL_H_
 
 #include <memory>
 #include <set>
 #include <string>
@@ skipping 75 matching lines @@
   // Idempotent, can be run any time later without impacting the current
   // schedule.
   void StopScheduling();
 
   // Trigger a background refetch for the given |trigger| if enabled and if the
   // timing is appropriate for another fetch.
   void RefetchInTheBackgroundIfAppropriate(TriggerType trigger);
 
   // Checks whether it is time to perform a soft background fetch, according to
   // |schedule|.
-  bool ShouldRefetchInTheBackgroundNow();
+  bool ShouldRefetchInTheBackgroundNow(base::Time last_fetch_attempt_time);
 
   // Returns whether background fetching (for the given |trigger|) is disabled.
   bool BackgroundFetchesDisabled(TriggerType trigger) const;
 
   // Returns true if quota is available for another request.
   bool AcquireQuota(bool interactive_request);
 
   // Callback after RefetchInTheBackground is completed.
   void RefetchInTheBackgroundFinished(Status fetch_status);
 
@@ skipping 30 matching lines @@
   bool background_fetch_in_progress_;
 
   // Used to adapt the schedule based on usage activity of the user. Not owned.
   const UserClassifier* user_classifier_;
 
   // Request throttlers for limiting requests for different classes of users.
   RequestThrottler request_throttler_rare_ntp_user_;
   RequestThrottler request_throttler_active_ntp_user_;
   RequestThrottler request_throttler_active_suggestions_consumer_;
 
+  // To make sure we only report the first trigger to UMA.
+  bool time_until_first_trigger_reported_;
+
   // We should not fetch in background before EULA gets accepted.
   std::unique_ptr<EulaState> eula_state_;
 
   PrefService* profile_prefs_;
   std::unique_ptr<base::Clock> clock_;
   std::set<TriggerType> enabled_triggers_;
 
   base::Time background_fetches_allowed_after_;
 
   DISALLOW_COPY_AND_ASSIGN(RemoteSuggestionsSchedulerImpl);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_SCHEDULER_IMPL_H_