[Sync] Initial implementation of foreign sessions suggestions provider.

components/ntp_snippets/features.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_FEATURES_H_
 #define COMPONENTS_NTP_SNIPPETS_FEATURES_H_
 
+#include <string>
+
 #include "base/feature_list.h"
 
 namespace ntp_snippets {
 
 // Features to turn individual providers/categories on/off.
 extern const base::Feature kArticleSuggestionsFeature;
 extern const base::Feature kBookmarkSuggestionsFeature;
 extern const base::Feature kRecentOfflineTabSuggestionsFeature;
 extern const base::Feature kDownloadSuggestionsFeature;
 extern const base::Feature kPhysicalWebPageSuggestionsFeature;
+extern const base::Feature kForeignSessionsSuggestionsFeature;
 
 // Feature to allow the 'save to offline' option to appear in the snippets
 // context menu.
 extern const base::Feature kSaveToOfflineFeature;
 
 // Global toggle for the whole content suggestions feature. If this is set to
 // false, all the per-provider features are ignored.
 extern const base::Feature kContentSuggestionsFeature;
 
+// Returns a feature param as an int instead of a string.
+int GetParamAsInt(const base::Feature& feature,
+                  const std::string& param_name,
+                  int default_value);
+
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_FEATURES_H_