Enable hovercard controller to send ajax ready responses

Summary: Refs T1048 - Resolves the TODO

Test Plan: Used in a future diff. Used JX.log to verify JSON format and correct gibberish HTML output of input (I will never understand how browsers can be so evil and ignore `Content-Type`).

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1048

Differential Revision: https://secure.phabricator.com/D5557

src/applications/search/controller/PhabricatorSearchHovercardController.php

@@ -54,10 +54,12 @@ final class PhabricatorSearchHovercardController
         array(
           'dust' => true,
         ));
+    } else {
+      return id(new AphrontAjaxResponse())->setContent(
+        array(
+          'cards' => $cards,
+        ));
     }
-
-    // TODO: Write a reasonable way to provide client-side-ready hovercard
-    // put-into-the-browser markup (coming in the next diff)
   }
 
 }