Add about flag for offline page experiment

components/offline_pages/offline_page_switches.cc

Index: components/offline_pages/offline_page_switches.cc
diff --git a/components/offline_pages/offline_page_switches.cc b/components/offline_pages/offline_page_switches.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2a24c35c0c6cb843b59ae4cf44d23325dc1f35bf
--- /dev/null
+++ b/components/offline_pages/offline_page_switches.cc
@@ -0,0 +1,15 @@
+// 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_switches.h"
+
+namespace switches {
+
+// Enable Offline Pages.
+const char kEnableOfflinePages[] = "enable-offline-pages";
+
+// Disable Offline Pages.
+const char kDisableOfflinePages[] = "disable-offline-pages";
+
+}  // namespace switches