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 fa957ef61d42ff3e56837a359519e39d0f0516ae..adaf87060a0ca0fe49d6ebcda09306deaa463d43 100644
--- a/ui/views/controls/combobox/combobox.cc
+++ b/ui/views/controls/combobox/combobox.cc
@@ -91,6 +91,7 @@ class TransparentButton : public CustomButton {
  public:
   TransparentButton(ButtonListener* listener)
       : CustomButton(listener) {
+    SetAccessibilityFocusable(false);

[tapted, 2016/02/12 02:56:44]

perhaps DCHECK(!IsFocusable());  after this? It's subtle that LabelButtons are
by-default focusable, but not CustomButtons

[karandeepb, 2016/02/22 07:15:37]

Done.

     SetAnimationDuration(LabelButton::kHoverAnimationDurationMs);
   }
   ~TransparentButton() override {}
@@ -350,7 +351,14 @@ Combobox::Combobox(ui::ComboboxModel* model)
       arrow_button_(new TransparentButton(this)),
       weak_ptr_factory_(this) {
   ModelChanged();
+
+#if !defined(OS_MACOSX)
   SetFocusable(true);
+#else
+  SetFocusable(false);
+  SetAccessibilityFocusable(true);
+#endif
+
   UpdateBorder();
 
   // Initialize the button images.
@@ -375,8 +383,6 @@ 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_);
 }