[evita] ui: Rename |ui::Widget::shown_| to |ui::Widget::visible_| and get rid of redundant |DidHide()| and |DidShow()| calls.
[evita] ui: Introduce |ui::Widget::GetLocalBounds()| and utilize it.
[evita] ui: Introudce |ui::SystemMetrics::icon_font_family()| and |icon_font_size()| and utilize it in |views::TabStrip| class.
[evita] ui/controls: Tidying up |ui::TextFieldControl|.