Let Ubertoken Fetch be primed with an access token.

google_apis/gaia/ubertoken_fetcher.h

Index: google_apis/gaia/ubertoken_fetcher.h
diff --git a/google_apis/gaia/ubertoken_fetcher.h b/google_apis/gaia/ubertoken_fetcher.h
index 54835e1d00102f9594294ccca0a54dbe1307f633..c74aa6c5b2e8c5fc576f23020063dcb4746ca633 100644
--- a/google_apis/gaia/ubertoken_fetcher.h
+++ b/google_apis/gaia/ubertoken_fetcher.h
@@ -50,6 +50,8 @@ class UbertokenFetcher : public GaiaAuthConsumer,
 
   // Start fetching the token for |account_id|.
   virtual void StartFetchingToken(const std::string& account_id);
+  virtual void StartFetchingTokenWithAccessToken(const std::string& account_id,

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

This does special stuff if access_token.empty() == true. I think this is a poor
API choice, so I'd either change the caller so they call StartFetchingToken()
instead, or else document this behavior.

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

Changed, per your other comment, so that this no longer has special behaviour if
access_token.empty(). We just DCHECK(!empty()).

+      const std::string& access_token);
 
   // Overriden from GaiaAuthConsumer
   void OnUberAuthTokenSuccess(const std::string& token) override;