Add more accessibility labels for screen readers

Summary:
Depends on D19594. See PHI823. Ref T13164.

  - Add a label for the "X" button in comment areas, like "Remove Action: Change Subscribers".
  - Add a label for the floating header display options menu in Differential.
  - Add `role="button"` to `PHUIButtonView` objects that we render with an `<a ...>` tag.

Test Plan:
Viewed a revision with `?__aural__=true`:

  - Saw "Remove Action: ..." label.
  - Saw "Display Options" label.
  - Used inspector to verify that some `<a class="button" ...>` now have `<a class="button" role="button" ...>`. This isn't exhaustive, but at least improves things. A specific example is the "edit", "reply", etc., actions on inline comments.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13164

Differential Revision: https://secure.phabricator.com/D19595

src/applications/differential/view/DifferentialChangesetListView.php

@@ -309,6 +309,7 @@ final class DifferentialChangesetListView extends AphrontView {
         'Show All Inlines' => pht('Show All Inlines'),
 
         'List Inline Comments' => pht('List Inline Comments'),
+        'Display Options' => pht('Display Options'),
 
         'Hide or show all inline comments.' =>
           pht('Hide or show all inline comments.'),

src/applications/transactions/view/PhabricatorApplicationTransactionCommentView.php

@@ -319,14 +319,18 @@ class PhabricatorApplicationTransactionCommentView extends AphrontView {
 
       foreach ($comment_actions as $key => $comment_action) {
         $key = $comment_action->getKey();
+        $label = $comment_action->getLabel();
+
+
         $action_map[$key] = array(
           'key' => $key,
-          'label' => $comment_action->getLabel(),
+          'label' => $label,
           'type' => $comment_action->getPHUIXControlType(),
           'spec' => $comment_action->getPHUIXControlSpecification(),
           'initialValue' => $comment_action->getInitialValue(),
           'groupKey' => $comment_action->getGroupKey(),
           'conflictKey' => $comment_action->getConflictKey(),
+          'auralLabel' => pht('Remove Action: %s', $label),
         );
 
         $type_map[$key] = $comment_action;

src/view/phui/PHUIButtonView.php

@@ -233,6 +233,13 @@ final class PHUIButtonView extends AphrontTagView {
       $classes = array();
     }
 
+    // See PHI823. If we aren't rendering a "<button>" tag, give the tag we
+    // are rendering a "button" role as a hint to screen readers.
+    $role = null;
+    if ($this->tag !== 'button') {
+      $role = 'button';
+    }
+
     return array(
       'class'  => $classes,
       'href'   => $this->href,
@@ -240,6 +247,7 @@ final class PHUIButtonView extends AphrontTagView {
       'title'  => $this->title,
       'sigil'  => $sigil,
       'meta'   => $meta,
+      'role' => $role,
     );
   }