MacViews: Implement Full Keyboard Access.

ui/views/controls/combobox/combobox.cc

Index: ui/views/controls/combobox/combobox.cc
diff --git a/ui/views/controls/combobox/combobox.cc b/ui/views/controls/combobox/combobox.cc
index 22512ea926c9607c8e663079041c636440412420..4d45cef24c8f50d9e7c433b5e91db35eaf48ca70 100644
--- a/ui/views/controls/combobox/combobox.cc
+++ b/ui/views/controls/combobox/combobox.cc
@@ -37,6 +37,7 @@
 #include "ui/views/mouse_constants.h"
 #include "ui/views/painter.h"
 #include "ui/views/resources/grit/views_resources.h"
+#include "ui/views/style/platform_style.h"
 #include "ui/views/widget/widget.h"
 
 namespace views {
@@ -91,6 +92,9 @@ class TransparentButton : public CustomButton {
  public:
   TransparentButton(ButtonListener* listener)
       : CustomButton(listener) {
+    SetAccessibilityFocusable(false);
+    DCHECK(!IsFocusable());
+
     SetAnimationDuration(LabelButton::kHoverAnimationDurationMs);
   }
   ~TransparentButton() override {}
@@ -350,7 +354,7 @@ Combobox::Combobox(ui::ComboboxModel* model)
       arrow_button_(new TransparentButton(this)),
       weak_ptr_factory_(this) {
   ModelChanged();
-  SetFocusable(true);
+  PlatformStyle::SetControlStyleFocus(this);
   UpdateBorder();
 
   // Initialize the button images.
@@ -375,8 +379,6 @@ Combobox::Combobox(ui::ComboboxModel* model)
 
   text_button_->SetVisible(true);
   arrow_button_->SetVisible(true);
-  text_button_->SetFocusable(false);
-  arrow_button_->SetFocusable(false);
   AddChildView(text_button_);
   AddChildView(arrow_button_);
 }