Show which capability is being edited in custom policy dialog

Summary: Fixes T7867.

Test Plan: {F392844}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7867

Differential Revision: https://secure.phabricator.com/D12716

src/view/form/control/AphrontFormPolicyControl.php

@@ -179,6 +179,7 @@ final class AphrontFormPolicyControl extends AphrontFormControl {
         'icons' => $icons,
         'labels' => $labels,
         'value' => $this->getValue(),
+        'capability' => $this->capability,
         'customPlaceholder' => $this->getCustomPolicyPlaceholder(),
       ));