Rollback option put behind the flag.

chromeos/chromeos_switches.cc

Index: chromeos/chromeos_switches.cc
diff --git a/chromeos/chromeos_switches.cc b/chromeos/chromeos_switches.cc
index 6478063d299890b67a0ab737ee7e1c65e428d3d8..77cf81ba93670c963f17511f9aae0f38bc5648fb 100644
--- a/chromeos/chromeos_switches.cc
+++ b/chromeos/chromeos_switches.cc
@@ -90,6 +90,9 @@ const char kEnableTouchpadThreeFingerClick[]
 // than the kiosk app mode.
 const char kEnableKioskMode[]               = "enable-kiosk-mode";
 
+// Enables rollback option for resetting ChromeOS.
+const char kEnableRollbackOption[]          = "enable-rollback-option";
+
 // Enables request of tablet site (via user agent override).
 const char kEnableRequestTabletSite[]       = "enable-request-tablet-site";