Measure usage metrics to prepare for adaptive fetching rates in M55

components/ntp_snippets/pref_names.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_PREF_NAMES_H_
 #define COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_
 
 namespace ntp_snippets {
 namespace prefs {
 
@@ skipping 17 matching lines @@
 // The pref name for the current day for the counter of requests for article
 // thumbnails.
 extern const char kSnippetThumbnailsRequestsDay[];
 
 extern const char kDismissedRecentOfflineTabSuggestions[];
 extern const char kDismissedDownloadSuggestions[];
 
 // The pref name for the time when M54 was first started on the device.
 extern const char kBookmarksFirstM54Start[];
 
+// The pref name for the discounted average number of browsing sessions per hour
+// that involve opening a new NTP.
+extern const char kUserClassifierAverageNTPOpenedPerHour[];
+// The pref name for the discounted average number of browsing sessions per hour
+// that involve opening showing the content suggestions.
+extern const char kUserClassifierAverageSuggestionsShownPerHour[];
+// The pref name for the discounted average number of browsing sessions per hour
+// that involve using content suggestions (i.e. opening one or clicking on the
+// "More" button).
+extern const char kUserClassifierAverageSuggestionsUsedPerHour[];
+
+// The pref name for the last time a new NTP was opened.
+extern const char kUserClassifierLastTimeToOpenNTP[];
+// The pref name for the last time content suggestions were shown to the user.
+extern const char kUserClassifierLastTimeToShowSuggestions[];
+// The pref name for the last time content suggestions were used by the user.
+extern const char kUserClassifierLastTimeToUseSuggestions[];
+
 }  // namespace prefs
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_