Clear old ARC instance before opt-in.

components/arc/user_data/arc_user_data_service.h

 // 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.
 
 #ifndef COMPONENTS_ARC_USER_DATA_ARC_USER_DATA_SERVICE_H_
 #define COMPONENTS_ARC_USER_DATA_ARC_USER_DATA_SERVICE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "components/arc/arc_bridge_service.h"
 #include "components/arc/arc_service.h"
+#include "components/prefs/pref_change_registrar.h"
 #include "components/prefs/pref_member.h"
 #include "components/signin/core/account_id/account_id.h"
 
+class PrefService;
+
 namespace arc {
 
 class ArcBridgeService;
 
 // This class controls the lifecycle of ARC user data, removing it when
 // necessary.
 class ArcUserDataService : public ArcService,
                            public ArcBridgeService::Observer {
  public:
   explicit ArcUserDataService(
       ArcBridgeService* arc_bridge_service,
       std::unique_ptr<BooleanPrefMember> arc_enabled_pref,
+      PrefService* pref_service,
       const AccountId& account_id);
   ~ArcUserDataService() override;
 
   // ArcBridgeService::Observer:
   // Called whenever the arc bridge is stopped to potentially remove data if
   // the user has not opted in.
   void OnBridgeStopped(ArcBridgeService::StopReason reason) override;
 
  private:
   base::ThreadChecker thread_checker_;
 
   // Checks if ARC is both stopped and disabled (not opt-in) and triggers
   // removal of user data if both conditions are true.
   void ClearIfDisabled();
 
+  // Callback when the kArcEnabled preference changes.  It watches for instances
+  // where the preference is disabled and remembers this so that it can wipe
+  // user data once the bridge has stopped.
+  void OnOptInPreferenceChanged();
+
   const std::unique_ptr<BooleanPrefMember> arc_enabled_pref_;
 
   // Account ID for the account for which we currently have opt-in information.
   AccountId primary_user_account_id_;
 
+  // Registrar used to monitor ARC enabled state.
+  PrefChangeRegistrar pref_change_registrar_;
+
+  // Set to true when kArcEnabled goes from true to false and set to false
+  // again after user data has been wiped.  This ensures data is wiped even if
+  // the user tries to enable ARC before the bridge has shut down.
+  bool arc_disabled_ = false;
+
+  base::WeakPtrFactory<ArcUserDataService> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ArcUserDataService);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_USER_DATA_ARC_USER_DATA_SERVICE_H_