Add an experimental flag for offlining.

components/offline_pages/offline_page_feature.h

 // Copyright 2015 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_OFFLINE_PAGES_OFFLINE_PAGE_FEATURE_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_FEATURE_H_
 
 #include "base/feature_list.h"
 #include "build/build_config.h"
 
 namespace offline_pages {
 
 extern const base::Feature kOfflineBookmarksFeature;
 extern const base::Feature kOffliningRecentPagesFeature;
 extern const base::Feature kOfflinePagesBackgroundLoadingFeature;
+extern const base::Feature kOfflinePagesCTFeature;
 
 // Returns true if offline pages, as result of one or more offline features
 // being enabled, is enabled.
 bool IsOfflinePagesEnabled();
 
 // Returns true if saving bookmarked pages for offline viewing is enabled.
 bool IsOfflineBookmarksEnabled();
 
 // Returns true if offlining of recent pages (aka 'Last N pages') is enabled.
 bool IsOffliningRecentPagesEnabled();
 
 // Returns true if saving offline pages in the background is enabled.
 bool IsOfflinePagesBackgroundLoadingEnabled();
 
+// Returns true if offline CT features are enabled.  See crbug.com/620421.
+bool IsOfflinePagesCTEnabled();
+
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_FEATURE_H_