MacViews a11y: Support the "Show menu" action in Textfield and Combobox.

ui/views/controls/combobox/combobox.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/controls/combobox/combobox.h"
 
 #include <stddef.h>
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "build/build_config.h"
+#include "ui/accessibility/ax_action_data.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/default_style.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/models/combobox_model_observer.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/events/event.h"
 #include "ui/gfx/animation/throb_animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_palette.h"
@@ skipping 735 matching lines @@
   node_data->SetName(accessible_name_);
   node_data->SetValue(model_->GetItemAt(selected_index_));
   if (enabled()) {
     node_data->AddIntAttribute(ui::AX_ATTR_DEFAULT_ACTION_VERB,
                                ui::AX_DEFAULT_ACTION_VERB_OPEN);
   }
   node_data->AddIntAttribute(ui::AX_ATTR_POS_IN_SET, selected_index_);
   node_data->AddIntAttribute(ui::AX_ATTR_SET_SIZE, model_->GetItemCount());
 }
 
+bool Combobox::HandleAccessibleAction(const ui::AXActionData& action_data) {
+  // The action handling in View would generate a mouse event and send it to
+  // |this|. However, mouse events for Combobox are handled by |arrow_button_|,
+  // which is hidden from the a11y tree (so can't expose actions). Rather than
+  // forwarding AX_ACTION_DO_DEFAULT to View and then forwarding the mouse event
+  // it generates to |arrow_button_| to have it forward back to |this| (as its
+  // ButtonListener), just handle the action explicitly here and bypass View.
+  if (enabled() && action_data.action == ui::AX_ACTION_DO_DEFAULT) {
+    ShowDropDownMenu(ui::MENU_SOURCE_KEYBOARD);
+    return true;
+  }
+  return View::HandleAccessibleAction(action_data);
+}
+
 void Combobox::ButtonPressed(Button* sender, const ui::Event& event) {
   if (!enabled())
     return;
 
   if (!UseMd())
     RequestFocus();
 
   if (sender == text_button_) {
     OnPerformAction();
   } else {
@@ skipping 235 matching lines @@
   constexpr int kMdPaddingWidth = 8;
   constexpr int kNormalPaddingWidth = 7;
   int arrow_pad = UseMd() ? kMdPaddingWidth : kNormalPaddingWidth;
   int padding = style_ == STYLE_NORMAL
                     ? arrow_pad * 2
                     : kActionLeftPadding + kActionRightPadding;
   return ArrowSize().width() + padding;
 }
 
 }  // namespace views