Makes Chrome's app menu have a vertical orientation.

ui/accessibility/ax_enums.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // TODO(nektar): Migrate entire file to Mojoq.
 // These should be kept in sync with third_party/WebKit/public/web/WebAXEnums.h
 // until the Chromium and Blink trees are merged.
 [camel_case_enum_to_string=true] namespace ui {
 
   // For new entries to the following three enums, also add to
@@ skipping 192 matching lines @@
   enum AXState {
     busy,
     checked,
     collapsed,
     default,
     disabled,
     editable,
     expanded,
     focusable,
     haspopup,
-    horizontal,
+    horizontal,  // Grows horizontally, e.g. most toolbars and separators.

[dmazzoni, 2016/10/14 19:37:20]

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     hovered,
     invisible,
     linked,
     multiline,
     multiselectable,
     offscreen,
     pressed,
     protected,
     read_only,
     required,
     richly_editable,
     selectable,
     selected,
-    vertical,
+    vertical,  // Grows vertically, e.g. menu or combo box.
     visited
   };
 
   // A change to the accessibility tree.
   enum AXMutation {
     node_created,
     subtree_created,
     node_changed,
     node_removed
   };
@@ skipping 310 matching lines @@
     // First node is before the second one.
     before,
 
     // Nodes are the same.
     equal,
 
     // First node is after the second one.
     after
   };
 };