cros: Fix EasyUnlockServiceSignin::OnUserDataLoaded crash.

chrome/browser/signin/easy_unlock_service_signin_chromeos.cc

Index: chrome/browser/signin/easy_unlock_service_signin_chromeos.cc
diff --git a/chrome/browser/signin/easy_unlock_service_signin_chromeos.cc b/chrome/browser/signin/easy_unlock_service_signin_chromeos.cc
index 4fd94240095d84f57b2d6fa69e0a6335fda6d500..7fb3809b40603146b46376324c714c7289ee1a32 100644
--- a/chrome/browser/signin/easy_unlock_service_signin_chromeos.cc
+++ b/chrome/browser/signin/easy_unlock_service_signin_chromeos.cc
@@ -333,6 +333,10 @@ 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_];