[Background fetching] Background fetching when opening an NTP.

components/ntp_snippets/pref_names.h

Index: components/ntp_snippets/pref_names.h
diff --git a/components/ntp_snippets/pref_names.h b/components/ntp_snippets/pref_names.h
index 5ff759f0d6982a7817159e74ee36fd818272c93b..f4a9ff7372c1187625a25ecfb441412a7eb26b84 100644
--- a/components/ntp_snippets/pref_names.h
+++ b/components/ntp_snippets/pref_names.h
@@ -16,6 +16,14 @@ extern const char kEnableSnippets[];
 // and title) are stored.
 extern const char kRemoteSuggestionCategories[];
 
+// The pref name for the soonest moment when the next soft background (active)
+// fetch may occur.
+extern const char kSnippetNextActiveSoftFetch[];
+// The pref name for the currently applied minimal interval between two
+// successive soft background fetches that react to user activity (such as
+// opening an NTP).
+extern const char kSnippetSoftFetchingIntervalActive[];
+
 // The pref name for the currently-scheduled background fetching interval when
 // there is WiFi connectivity.
 extern const char kSnippetBackgroundFetchingIntervalWifi[];