Clear old ARC instance before opt-in.

components/arc/user_data/arc_user_data_service.cc

 // Copyright 2016 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/arc/user_data/arc_user_data_service.h"
 
 #include <utility>
 
 #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"
 #include "components/prefs/pref_member.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user_manager.h"
 
 namespace arc {
 
 ArcUserDataService::ArcUserDataService(
     ArcBridgeService* bridge_service,
     std::unique_ptr<BooleanPrefMember> arc_enabled_pref,
+    PrefService* pref_service,
     const AccountId& account_id)
     : ArcService(bridge_service),
       arc_enabled_pref_(std::move(arc_enabled_pref)),
-      primary_user_account_id_(account_id) {
+      primary_user_account_id_(account_id),
+      weak_ptr_factory_(this) {
   arc_bridge_service()->AddObserver(this);
+  pref_change_registrar_.Init(pref_service);

[hidehiko, 2016/07/15 14:39:23]

arc_enabled_pref_->prefs() should work?

+  pref_change_registrar_.Add(
+      arc_enabled_pref_->GetPrefName(),
+      base::Bind(&ArcUserDataService::OnOptInPreferenceChanged,
+                 weak_ptr_factory_.GetWeakPtr()));
   ClearIfDisabled();
 }
 
 ArcUserDataService::~ArcUserDataService() {
   DCHECK(thread_checker_.CalledOnValidThread());
   arc_bridge_service()->RemoveObserver(this);
 }
 
 void ArcUserDataService::OnBridgeStopped(ArcBridgeService::StopReason reason) {
   DCHECK(thread_checker_.CalledOnValidThread());
   const AccountId& account_id =
       user_manager::UserManager::Get()->GetPrimaryUser()->GetAccountId();
   if (account_id != primary_user_account_id_) {
     LOG(ERROR) << "User preferences not loaded for "
                << primary_user_account_id_.GetUserEmail()
                << ", but current primary user is " << account_id.GetUserEmail();
     primary_user_account_id_ = EmptyAccountId();
     return;
   }
   ClearIfDisabled();
 }
 
 void ArcUserDataService::ClearIfDisabled() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!arc_bridge_service()->stopped()) {
     LOG(ERROR) << "ARC instance not stopped, user data can't be cleared";
     return;
   }
-  if (arc_enabled_pref_->GetValue() ||
+  if ((arc_enabled_pref_->GetValue() && !arc_disabled_) ||
       base::CommandLine::ForCurrentProcess()->HasSwitch(
           chromeos::switches::kDisableArcDataWipe)) {
     return;
   }
+  arc_disabled_ = false;
   const cryptohome::Identification cryptohome_id(primary_user_account_id_);
   chromeos::SessionManagerClient* session_manager_client =
       chromeos::DBusThreadManager::Get()->GetSessionManagerClient();
   session_manager_client->RemoveArcData(cryptohome_id);
 }
 
+void ArcUserDataService::OnOptInPreferenceChanged() {
+  if (!arc_enabled_pref_->GetValue())
+    arc_disabled_ = true;
+}
+
 }  // namespace arc