Add a disable-arc-data-wipe flag.

components/arc/user_data/arc_user_data_service.cc

Index: components/arc/user_data/arc_user_data_service.cc
diff --git a/components/arc/user_data/arc_user_data_service.cc b/components/arc/user_data/arc_user_data_service.cc
index 27d42d729bc0b27044c87efc9241460aa2916e5c..5284352dea2ec8ad352d06c2b1720b92300fad5d 100644
--- a/components/arc/user_data/arc_user_data_service.cc
+++ b/components/arc/user_data/arc_user_data_service.cc
@@ -4,6 +4,8 @@
 
 #include "components/arc/user_data/arc_user_data_service.h"
 
+#include "base/command_line.h"
+#include "chromeos/chromeos_switches.h"
 #include "chromeos/cryptohome/cryptohome_parameters.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
@@ -49,7 +51,9 @@ void ArcUserDataService::ClearIfDisabled() {
     LOG(ERROR) << "ARC instance not stopped, user data can't be cleared";
     return;
   }
-  if (arc_enabled_pref_->GetValue())
+  if (arc_enabled_pref_->GetValue() ||
+      base::CommandLine::ForCurrentProcess()->HasSwitch(
+          chromeos::switches::kDisableArcDataWipe))

[Yusuke Sato, 2016/07/05 03:52:41]

nit: can you add {}? IIUC arc/ usually uses {} when the condition is multi-line.

[dspaid, 2016/07/05 03:59:04]

Done.

     return;
   const cryptohome::Identification cryptohome_id(primary_user_account_id_);
   chromeos::SessionManagerClient* session_manager_client =