[EasyUnlock] Fix crash when the same user pod is refocused.

components/proximity_auth/proximity_auth_system_unittest.cc

 // Copyright 2014 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/proximity_auth/proximity_auth_system.h"
 
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/cryptauth/remote_device.h"
 #include "components/proximity_auth/fake_lock_handler.h"
@@ skipping 283 matching lines @@
   life_cycle = nullptr;
   EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(_))
       .WillOnce(SaveArg<0>(&life_cycle));
   FocusUser(kUser1);
   EXPECT_EQ(kUser1, life_cycle->GetRemoteDevice().user_id);
 
   EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(nullptr))
       .Times(AtLeast(1));
 }
 
+TEST_F(ProximityAuthSystemTest, ToggleFocus_SameUserRefocused) {
+  RemoteDeviceLifeCycle* life_cycle = nullptr;
+  EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(_))
+      .WillOnce(SaveArg<0>(&life_cycle));
+  FocusUser(kUser1);
+  EXPECT_EQ(kUser1, life_cycle->GetRemoteDevice().user_id);
+
+  // Focusing the user again should be idempotent. The screenlock UI may call
+  // focus on the same user multiple times.
+  // SetRemoteDeviceLifeCycle() is only expected to be called once.
+  FocusUser(kUser1);
+
+  // The RemoteDeviceLifeCycle should be nulled upon destruction.
+  EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(nullptr))
+      .Times(AtLeast(1));
+}
+
 TEST_F(ProximityAuthSystemTest, RestartSystem_UnregisteredUserFocused) {
   FocusUser(kUser2);
 
   EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(nullptr))
       .Times(AnyNumber());
   proximity_auth_system_->Stop();
   proximity_auth_system_->Start();
   EXPECT_FALSE(life_cycle());
 }
 
@@ skipping 53 matching lines @@
     SimulateSuspend();
   }
 
   EXPECT_EQ(kUser1, life_cycle()->GetRemoteDevice().user_id);
 
   EXPECT_CALL(*unlock_manager_, SetRemoteDeviceLifeCycle(nullptr))
       .Times(AtLeast(1));
 }
 
 }  // namespace proximity_auth