Show the customized "Login" message on the login screen

Summary: Depends on D19992. Ref T13222. If administrators provide a custom login message, show it on the login screen.

Test Plan:
{F6137930}

  - Viewed login screen with and without a custom message.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13222

Differential Revision: https://secure.phabricator.com/D19994

src/applications/auth/controller/PhabricatorAuthStartController.php

@@ -194,6 +194,8 @@ final class PhabricatorAuthStartController
       $invite_message = $this->renderInviteHeader($invite);
     }
 
+    $custom_message = $this->newCustomStartMessage();
+
     $crumbs = $this->buildApplicationCrumbs();
     $crumbs->addTextCrumb(pht('Login'));
     $crumbs->setBorder(true);
@@ -202,6 +204,7 @@ final class PhabricatorAuthStartController
     $view = array(
       $header,
       $invite_message,
+      $custom_message,
       $out,
     );
 
@@ -305,4 +308,25 @@ final class PhabricatorAuthStartController
       ->setURI($auto_uri);
   }
 
+  private function newCustomStartMessage() {
+    $viewer = $this->getViewer();
+
+    $text = PhabricatorAuthMessage::loadMessageText(
+      $viewer,
+      PhabricatorAuthLoginMessageType::MESSAGEKEY);
+
+    if (!strlen($text)) {
+      return null;
+    }
+
+    $remarkup_view = new PHUIRemarkupView($viewer, $text);
+
+    return phutil_tag(
+      'div',
+      array(
+        'class' => 'auth-custom-message',
+      ),
+      $remarkup_view);
+  }
+
 }