Add enable-offlining-recent-pages feature switch.

components/offline_pages/offline_page_feature.cc

Index: components/offline_pages/offline_page_feature.cc
diff --git a/components/offline_pages/offline_page_feature.cc b/components/offline_pages/offline_page_feature.cc
index beee145d8398d9618a126bcad5070aa3bbb0039c..f6b7dac57526cab19b58b50409d1eec491244726 100644
--- a/components/offline_pages/offline_page_feature.cc
+++ b/components/offline_pages/offline_page_feature.cc
@@ -71,6 +71,17 @@ bool IsOfflinePagesEnabled() {
          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