Add always-on-top property to app windows

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index 9261c7227d5f448a5f5083338c3b471e94275ff3..e7df069c18ee987aea95735addc1a72b52d13984 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -658,6 +658,10 @@ void Widget::SetAlwaysOnTop(bool on_top) {
   native_widget_->SetAlwaysOnTop(on_top);
 }
 
+bool Widget::IsAlwaysOnTop() const {
+  return native_widget_->IsAlwaysOnTop();
+}
+
 void Widget::Maximize() {
   native_widget_->Maximize();
 }