Make the authentication service remember selected usernames.

mojo/services/authentication/public/interfaces/authentication.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [JavaPackage="org.chromium.mojo.authentication"]
 module authentication;
 
 // Interface to handle user identity and authentication tokens.
 // TODO(qsr): This API only handles google accounts at this time. It will need
 //            to be extended to allow generic account manager on the platform.
 interface AuthenticationService {
   // Requests a Google account to use. In case of success, error will be null.
   // In case of error, username will be null and error will contain a
   // description of the error.
-  SelectAccount() => (string? username, string? error);
+  SelectAccount(bool returned_last_selected) =>

[tonyg, 2015/06/03 14:59:27]

s/returned/use/ or at least s/returned/return/?

Also, recommend updating comment.

[qsr, 2015/06/03 15:12:42]

Done.

+      (string? username, string? error);
 
   // Requests an oauth2 token for the given Google account with the given
   // scopes.  In case of error, username will be null and error will contain a
   // description of the error.
   GetOAuth2Token(string username, array<string> scopes) =>
       (string? token, string? error);
 
   // Requests to clear a previously acquired token. This should be called when a
   // token is refused by a server component before requesting a new token to
   // clear the token from any cache.
   ClearOAuth2Token(string token);
 };