cros: Fix EasyUnlockServiceSignin::OnUserDataLoaded crash.

chrome/browser/signin/easy_unlock_service_signin_chromeos.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 "chrome/browser/signin/easy_unlock_service_signin_chromeos.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 315 matching lines @@
       allow_cryptohome_backoff_ ? 0u : kMaxCryptohomeBackoffIntervalMs,
       base::Bind(&EasyUnlockServiceSignin::OnUserDataLoaded,
                  weak_ptr_factory_.GetWeakPtr(),
                  user_id_));
 }
 
 void EasyUnlockServiceSignin::OnUserDataLoaded(
     const std::string& user_id,
     bool success,
     const chromeos::EasyUnlockDeviceKeyDataList& devices) {
+  // Bail out if this is called after service shuts down.
+  if (!service_active_)

[tbarzic, 2015/02/24 19:51:07]

Won't invalidating weak ptrs in ShutDownInternal prevent this from being called
after service is shut down?
What am I missing?

[xiyuan, 2015/02/24 20:25:53]

You are right. The callback should not be called after ShutdownInternal.

The problem is probably because we are using |user_id_| to get data but it has
changed after we start to load data. One possible case is there is no focused
user when the callback is invoked. We should always user |user_id| that is
passed in with the callback.

+    return;
+
   allow_cryptohome_backoff_ = false;
 
   UserData* data = user_data_[user_id_];
   data->state = USER_DATA_STATE_LOADED;
   if (success) {
     data->devices = devices;
     chromeos::EasyUnlockKeyManager::DeviceDataListToRemoteDeviceList(
         user_id, devices, &data->remote_devices_value);
   }
 
   // If the fetched data belongs to the currently focused user, notify the app
   // that it has to refresh it's user data.
   if (user_id == user_id_)
     NotifyUserUpdated();
 }
 
 const EasyUnlockServiceSignin::UserData*
     EasyUnlockServiceSignin::FindLoadedDataForCurrentUser() const {
   if (user_id_.empty())
     return NULL;
 
   std::map<std::string, UserData*>::const_iterator it =
       user_data_.find(user_id_);
   if (it == user_data_.end())
     return NULL;
   if (it->second->state != USER_DATA_STATE_LOADED)
     return NULL;
   return it->second;
 }