MacViews: Implement Full Keyboard Access.

ui/views/controls/button/button.cc

Index: ui/views/controls/button/button.cc
diff --git a/ui/views/controls/button/button.cc b/ui/views/controls/button/button.cc
index 9f7e5e283c2542c0a24d6d96e2cc6bce7791add6..65ce865d977e76a97e1bec4ebc4f39d5ea579f2c 100644
--- a/ui/views/controls/button/button.cc
+++ b/ui/views/controls/button/button.cc
@@ -24,6 +24,16 @@ Button::ButtonState Button::GetButtonStateFrom(ui::NativeTheme::State state) {
   return Button::STATE_NORMAL;
 }
 
+// static
+void Button::ConfigureDefaultFocus(Button* button) {
+#if defined(OS_MACOSX)
+  // On Mac, buttons are focusable only in full keyboard access mode.
+  button->SetFocusBehavior(FocusBehavior::ACCESSIBLE_ONLY);
+#else
+  button->SetFocusBehavior(FocusBehavior::ALWAYS);
+#endif
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Button, public: