Fetch OAuth2 tokens prior to profile creation.

chrome/browser/chromeos/login/existing_user_controller.cc

Index: chrome/browser/chromeos/login/existing_user_controller.cc
diff --git a/chrome/browser/chromeos/login/existing_user_controller.cc b/chrome/browser/chromeos/login/existing_user_controller.cc
index ce08f36771da070ae3dbfda1040d72af7ae36b0d..a9fc52b859d7c7b18303d2d36979d33a752dcbce 100644
--- a/chrome/browser/chromeos/login/existing_user_controller.cc
+++ b/chrome/browser/chromeos/login/existing_user_controller.cc
@@ -1122,6 +1122,14 @@ void ExistingUserController::DoCompleteLogin(const UserContext& user_context) {
     return;
   }
 
+  if (!user_context.GetAuthCode().empty() &&
+      user_context.GetAuthFlow() == UserContext::AUTH_FLOW_GAIA_WITHOUT_SAML) {
+    UserSessionManager::GetInstance()->FetchOAuth2Tokens(

[xiyuan, 2015/04/20 22:02:41]

Prefer to put FetchOAuth2Tokens logic out of UserSessionManager because it is
already too big.

How about we have some helper similar to BootstrapUserContextInitializer that do
the token fetching and put the fetched tokens in UserContext (O2RT as well as
the oauthlogin_access_token). 

[achuithb, 2015/04/21 07:10:20]

Done.

+        user_context, base::Bind(&ExistingUserController::PerformLogin,
+                                 weak_factory_.GetWeakPtr()));
+    return;
+  }
+
   PerformLogin(user_context, LoginPerformer::AUTH_MODE_EXTENSION);
 }