[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_
 
+#include <set>
+#include <string>
+
+class PrefService;
+
 namespace ntp_snippets {
 namespace prefs {
 
 extern const char kEnableSnippets[];
 
 extern const char kSnippetHosts[];
 
 // 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[];
 // 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[];
 
+std::set<std::string> ReadDismissedIDsFromPrefs(const std::string& pref_name,
+                                                PrefService* pref_service);

[Marc Treib, 2016/08/29 09:18:50]

nit: const
nit²: Should |pref_service| be the first param?

[tschumann, 2016/08/29 09:39:15]

yeah, let's make |pref_service| a const reference and the first parameter.

[battre, 2016/08/29 09:48:26]

Do these functions belong into pref_names.h?

[skym, 2016/09/15 23:18:17]

Done. Done.

[skym, 2016/09/15 23:18:17]

Moved to their own file.

[skym, 2016/09/15 23:18:17]

Done.

+
+void StoreDismissedIDsToPrefs(const std::string& pref_name,
+                              const std::set<std::string>& dismissed_ids,
+                              PrefService* pref_service);
+
 }  // namespace prefs
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_