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

components/proximity_auth/proximity_auth_system_unittest.cc

Index: components/proximity_auth/proximity_auth_system_unittest.cc
diff --git a/components/proximity_auth/proximity_auth_system_unittest.cc b/components/proximity_auth/proximity_auth_system_unittest.cc
index 2d878b1ec506882f3d2f26d21f7b821402846377..26247a2c8d8ea81e8b7b3a3629ebbe6fff529ee1 100644
--- a/components/proximity_auth/proximity_auth_system_unittest.cc
+++ b/components/proximity_auth/proximity_auth_system_unittest.cc
@@ -301,6 +301,23 @@ TEST_F(ProximityAuthSystemTest, ToggleFocus_RegisteredAndUnregisteredUsers) {
       .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);