easy-unlock: Fix AttemptAuth email CHECK crash

chrome/browser/signin/easy_unlock_service.cc

Index: chrome/browser/signin/easy_unlock_service.cc
diff --git a/chrome/browser/signin/easy_unlock_service.cc b/chrome/browser/signin/easy_unlock_service.cc
index 5170566ad18c2ff6abb703b2a691a760a590085c..898e221f4affadcb878635a9c45868382fe65043 100644
--- a/chrome/browser/signin/easy_unlock_service.cc
+++ b/chrome/browser/signin/easy_unlock_service.cc
@@ -493,7 +493,13 @@ void EasyUnlockService::AttemptAuth(const std::string& user_id) {
 
 void EasyUnlockService::AttemptAuth(const std::string& user_id,
                                     const AttemptAuthCallback& callback) {
-  CHECK_EQ(GetUserEmail(), user_id);
+  const std::string user_email = GetUserEmail();
+  if (user_email.empty()) {
+    LOG(ERROR) << "Empty user email. Refresh token might go bad.";
+    return;

[Tim Song, 2015/05/21 00:06:46]

We should run the callback with a failure.

[xiyuan, 2015/05/21 01:32:12]

Good call. Done.

+  }
+
+  CHECK_EQ(user_email, user_id);
 
   auth_attempt_.reset(new EasyUnlockAuthAttempt(
       app_manager_.get(), user_id,