[Sync] Initial implementation of foreign sessions suggestions provider.

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 13 matching lines @@
 extern const char kSnippetThumbnailsRequestCount[];
 // The pref name for today's count of interactive requests for article
 // thumbnails, so far.
 extern const char kSnippetThumbnailsInteractiveRequestCount[];
 // 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[];
+extern const char kDismissedForeignSessionsSuggestions[];
 
 // 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_