[NTP Snippets] Don't reschedule background fetching on every startup

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 {
 
 extern const char kEnableSnippets[];
 
 extern const char kSnippetHosts[];
 
+// The pref name for the currently-scheduled background fetching interval when
+// there is WiFi connectivity.
+extern const char kSnippetBackgroundFetchingIntervalWifi[];
+// The pref name for the currently-scheduled background fetching interval when
+// there is no WiFi connectivity.
+extern const char kSnippetBackgroundFetchingIntervalFallback[];
+
 // The pref name for today's count of NTPSnippetsFetcher requests, so far.
 extern const char kSnippetFetcherRequestCount[];
 // The pref name for today's count of NTPSnippetsFetcher interactive requests.
 extern const char kSnippetFetcherInteractiveRequestCount[];
 // The pref name for the current day for the counter of NTPSnippetsFetcher
 // requests.
 extern const char kSnippetFetcherRequestsDay[];
 
 // The pref name for today's count of requests for article thumbnails, so far.
 extern const char kSnippetThumbnailsRequestCount[];
@@ skipping 26 matching lines @@
 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_