[NTP::Push] Add Content Suggestions GCM App Handler

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 76 matching lines @@
 
 // The pref name for the current order of categories and their clicks.
 extern const char kClickBasedCategoryRankerOrderWithClicks[];
 // The pref name for the time when last click decay has happened.
 extern const char kClickBasedCategoryRankerLastDecayTime[];
 
 // The pref name for the subscription token used when subscription for breaking
 // news push updates,
 extern const char kContentSuggestionsSubscriptionDataToken[];
 
+// The pref name for the subscription token received from the gcm server. As
+// recommended by the GCM team, it is cached in pref instead of being retrieved
+// over network every time the client subscribe to push updates.
+extern const char kContentSuggestionsGCMSubscriptionTokenCache[];
 }  // namespace prefs
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_