cros: Launch the Account Access help app from "Learn more" button.

Bug: 863620
Change-Id: Id15fc12e23ca4fd51b92454d27d87133120aee82
Reviewed-on: https://chromium-review.googlesource.com/1157249
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Commit-Queue: Quan Nguyen <qnnguyen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580332}

diff --git a/ash/login/login_screen_controller.cc b/ash/login/login_screen_controller.cc
index 7f52f9a..38d36f18 100644
--- a/ash/login/login_screen_controller.cc
+++ b/ash/login/login_screen_controller.cc

@@ -440,6 +440,10 @@
   login_screen_client_->ShowResetScreen();
 }
 
+void LoginScreenController::ShowAccountAccessHelpApp() {
+  login_screen_client_->ShowAccountAccessHelpApp();
+}
+
 void LoginScreenController::DoAuthenticateUser(const AccountId& account_id,
                                                const std::string& password,
                                                bool authenticated_by_pin,