Let Ubertoken Fetch be primed with an access token.

google_apis/gaia/ubertoken_fetcher.cc

Index: google_apis/gaia/ubertoken_fetcher.cc
diff --git a/google_apis/gaia/ubertoken_fetcher.cc b/google_apis/gaia/ubertoken_fetcher.cc
index 15e5932bed620498fe8ede7fc2cd6ad2369c987d..10f2ba286859188146ba5a634159e0dde2f77802 100644
--- a/google_apis/gaia/ubertoken_fetcher.cc
+++ b/google_apis/gaia/ubertoken_fetcher.cc
@@ -43,6 +43,17 @@ void UbertokenFetcher::StartFetchingToken(const std::string& account_id) {
   RequestAccessToken();
 }
 
+void UbertokenFetcher::StartFetchingTokenWithAccessToken(
+    const std::string& account_id, const std::string& access_token) {
+  DCHECK(!account_id.empty());
+  if (access_token.empty())

[Andrew T Wilson (Slow), 2015/05/11 10:06:21]

Adding a DCHECK() then handling this case seems bad. Just add your DCHECK() then
fall through with an empty access_token (you'll end up getting an auth error,
but that's OK - the access_token is invalid and there's no reason to treat
access_token == "" any differently than access_token == "foobar_invalid_token"

[Roger Tawa OOO till Jul 10th, 2015/05/11 16:56:16]

This code is DCHECKing one thing and handling another, so seems OK from that
point of view.  However, seems that if the access token is empty, this should
return after call to StartFetchingToken() as Xiyuan suggests.

Alternatively, do as Drew suggests and collapse
StartFetchingTokenWithAccessToken() into StartFetchingToken() and have only one
method that does the right thing depending on if an access token is given or
not.

[Andrew T Wilson (Slow), 2015/05/12 15:08:08]

Ah, you are right, I missed that one was checking account_id and the other was
checking access_token.

[Mike Lerman, 2015/05/12 20:51:44]

Changed this method so that it should always have both an access token and an
account_id.

+    StartFetchingToken(account_id);

[xiyuan, 2015/05/11 16:11:58]

Should we return here to let access token fetching finish?

[Mike Lerman, 2015/05/12 20:51:44]

I no longer permit access_token.empty(). The caller should call the other method
instead.

+
+  account_id_ = account_id;
+  access_token_ = access_token;
+  ExchangeTokens();
+}
+
 void UbertokenFetcher::OnUberAuthTokenSuccess(const std::string& token) {
   consumer_->OnUbertokenSuccess(token);
 }