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

ui/views/controls/combobox/combobox_unittest.cc

Index: ui/views/controls/combobox/combobox_unittest.cc
diff --git a/ui/views/controls/combobox/combobox_unittest.cc b/ui/views/controls/combobox/combobox_unittest.cc
index 31a0c159ddf6c5a6e87c883b8220c7f486878131..5b822f539cb2cea835b6fc715cbb64325fe33fd1 100644
--- a/ui/views/controls/combobox/combobox_unittest.cc
+++ b/ui/views/controls/combobox/combobox_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/macros.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
+#include "ui/accessibility/ax_action_data.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/models/combobox_model.h"
@@ -642,6 +643,29 @@ TEST_F(ComboboxTest, NotifyOnClickWithSpaceKey) {
   EXPECT_FALSE(listener.on_perform_action_called());
 }
 
+// Test that accessibility action events show the combobox dropdown.
+TEST_F(ComboboxTest, ShowViaAccessibleAction) {
+  InitCombobox(nullptr, Combobox::STYLE_NORMAL);
+
+  ui::AXActionData data;
+  data.action = ui::AX_ACTION_DO_DEFAULT;
+  combobox_->HandleAccessibleAction(data);
+  EXPECT_EQ(1, menu_show_count_);
+
+  combobox_->SetEnabled(false);
+  combobox_->HandleAccessibleAction(data);
+  EXPECT_EQ(1, menu_show_count_);  // No change.
+
+  combobox_->SetEnabled(true);
+  data.action = ui::AX_ACTION_SHOW_CONTEXT_MENU;
+  combobox_->HandleAccessibleAction(data);
+  EXPECT_EQ(2, menu_show_count_);
+
+  data.action = ui::AX_ACTION_BLUR;
+  combobox_->HandleAccessibleAction(data);
+  EXPECT_EQ(2, menu_show_count_);  // No change.
+}
+
 TEST_F(ComboboxTest, NotifyOnClickWithSpaceKeyActionStyle) {
   InitCombobox(nullptr, Combobox::STYLE_ACTION);