Add enable-offlining-recent-pages feature switch.

components/offline_pages/offline_page_feature.cc

 // 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.
 
 #include "components/offline_pages/offline_page_feature.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
@@ skipping 53 matching lines @@
   }
   return FeatureMode::DISABLED;
 }
 
 bool IsOfflinePagesEnabled() {
   FeatureMode mode = GetOfflinePageFeatureMode();
   return mode == FeatureMode::ENABLED_AS_BOOKMARKS ||
          mode == FeatureMode::ENABLED_AS_SAVED_PAGES;
 }
 
+bool IsOffliningRecentPagesEnabled() {
+  bool hasDisableSwitch = base::CommandLine::ForCurrentProcess()->HasSwitch(

[jianli, 2016/03/02 00:52:31]

nit: C++ style

+        switches::kDisableOffliningRecentPages);
+  bool hasEnableSwitch = base::CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kEnableOffliningRecentPages);
+
+  // Default is 'disable'.
+  return !hasDisableSwitch && hasEnableSwitch && IsOfflinePagesEnabled();
+}
+
+
 }  // namespace offline_pages
 
 #endif