Add tokeninfo call with token identified by token_handle parameter.

google_apis/gaia/gaia_oauth_client.h

Index: google_apis/gaia/gaia_oauth_client.h
diff --git a/google_apis/gaia/gaia_oauth_client.h b/google_apis/gaia/gaia_oauth_client.h
index 68eb7665bcd1bdba3ecd7402988e293518db759f..e3ecd0dafc59e7b6bf2fe801ad63c334a4a3c87c 100644
--- a/google_apis/gaia/gaia_oauth_client.h
+++ b/google_apis/gaia/gaia_oauth_client.h
@@ -128,6 +128,14 @@ class GaiaOAuthClient {
                     int max_retries,
                     Delegate* delegate);
 
+  // Call the tokeninfo API for given |token_handle|, returning a dictionary of
+  // response values. Basic results will be returned via
+  // |OnGetTokenInfoResponse| call: audience, expires_in, user_id. See
+  // |max_retries| docs above.
+  void GetTokenHandleInfo(const std::string& token_handle,
+                          int max_retries,
+                          Delegate* delegate);
+
  private:
   // The guts of the implementation live in this class.
   class Core;