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

components/proximity_auth/proximity_auth_system.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/threading/thread_task_runner_handle.h"
 #include "components/proximity_auth/logging/logging.h"
 #include "components/proximity_auth/proximity_auth_client.h"
 #include "components/proximity_auth/remote_device_life_cycle_impl.h"
@@ skipping 109 matching lines @@
   OnFocusedUserChanged(ScreenlockBridge::Get()->focused_account_id());
 }
 
 void ProximityAuthSystem::OnScreenDidUnlock(
     ScreenlockBridge::LockHandler::ScreenType screen_type) {
   unlock_manager_->SetRemoteDeviceLifeCycle(nullptr);
   remote_device_life_cycle_.reset();
 }
 
 void ProximityAuthSystem::OnFocusedUserChanged(const AccountId& account_id) {
-  if (!account_id.is_valid())
-    return;
-
   // Update the current RemoteDeviceLifeCycle to the focused user.
-  if (remote_device_life_cycle_ &&
-      remote_device_life_cycle_->GetRemoteDevice().user_id !=
-          account_id.GetUserEmail()) {
-    PA_LOG(INFO) << "Focused user changed, destroying life cycle for "
-                 << account_id.Serialize() << ".";
-    unlock_manager_->SetRemoteDeviceLifeCycle(nullptr);
-    remote_device_life_cycle_.reset();
+  if (remote_device_life_cycle_) {
+    if (remote_device_life_cycle_->GetRemoteDevice().user_id !=
+        account_id.GetUserEmail()) {
+      PA_LOG(INFO) << "Focused user changed, destroying life cycle for "
+                   << account_id.Serialize() << ".";
+      unlock_manager_->SetRemoteDeviceLifeCycle(nullptr);
+      remote_device_life_cycle_.reset();
+    } else {
+      PA_LOG(INFO) << "Refocused on a user who is already focused.";
+      return;
+    }
   }
 
   if (remote_devices_map_.find(account_id) == remote_devices_map_.end() ||
       remote_devices_map_[account_id].size() == 0) {
     PA_LOG(INFO) << "User " << account_id.Serialize()
                  << " does not have a RemoteDevice.";
     return;
   }
 
   // TODO(tengs): We currently assume each user has only one RemoteDevice, so we
   // can simply take the first item in the list.
   cryptauth::RemoteDevice remote_device = remote_devices_map_[account_id][0];
   if (!suspended_) {
     PA_LOG(INFO) << "Creating RemoteDeviceLifeCycle for focused user: "
                  << account_id.Serialize();
     remote_device_life_cycle_ = CreateRemoteDeviceLifeCycle(remote_device);
     unlock_manager_->SetRemoteDeviceLifeCycle(remote_device_life_cycle_.get());
     remote_device_life_cycle_->AddObserver(this);
     remote_device_life_cycle_->Start();
   }
 }
 
 }  // proximity_auth