Remove explicit singletonness of ArcBridgeService part 4.

chrome/browser/chromeos/arc/arc_session_manager.h

Index: chrome/browser/chromeos/arc/arc_session_manager.h
diff --git a/chrome/browser/chromeos/arc/arc_session_manager.h b/chrome/browser/chromeos/arc/arc_session_manager.h
index 79f590f4108bcec72b4ff43f2ccc4f4e53e499c1..5c6a16e759de31556166ac3b5dbf846a999b6347 100644
--- a/chrome/browser/chromeos/arc/arc_session_manager.h
+++ b/chrome/browser/chromeos/arc/arc_session_manager.h
@@ -206,6 +206,8 @@ class ArcSessionManager : public ArcService,
 
   void OnProvisioningFinished(ProvisioningResult result);
 
+  void SetAttemptUserExitCallbackForTesting(const base::Closure& callback);
+
  private:
   // Negotiates the terms of service to user.
   void StartTermsOfServiceNegotiation();
@@ -254,6 +256,7 @@ class ArcSessionManager : public ArcService,
   std::unique_ptr<ArcAndroidManagementChecker> android_management_checker_;
 
   base::Time sign_in_time_;
+  base::Closure attempt_user_exit_callback_;
 
   base::WeakPtrFactory<ArcSessionManager> weak_ptr_factory_;