[gnome-games/gnome-3-36] ui: Add HeaderBarWidget

[Alexander Mikhaylenko <alexm src gnome org>]

commit a63b09a35a00c3f5e4dc6ecf61b082ca1293aee3
Author: sevagen <sevagenv gmail com>
Date:   Tue Feb 18 13:23:11 2020 +0530

    ui: Add HeaderBarWidget
    
    This interface will allow extra widgets added by plugins to block headerbar
    autohide when they have open popovers.

 src/meson.build               | 1 +
 src/ui/header-bar-widget.vala | 5 +++++
 2 files changed, 6 insertions(+)
---
diff --git a/src/meson.build b/src/meson.build
index c751641c..284cd2d9 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -120,6 +120,7 @@ vala_sources = [
   'ui/game-icon-view.vala',
   'ui/game-thumbnail.vala',
   'ui/gamepad-view-configuration.vala',
+  'ui/header-bar-widget.vala',
   'ui/input-mode-switcher.vala',
   'ui/keyboard-mapper.vala',
   'ui/keyboard-tester.vala',
diff --git a/src/ui/header-bar-widget.vala b/src/ui/header-bar-widget.vala
new file mode 100644
index 00000000..ecbde676
--- /dev/null
+++ b/src/ui/header-bar-widget.vala
@@ -0,0 +1,5 @@
+// This file is part of GNOME Games. License: GPL-3.0+.
+
+public interface Games.HeaderBarWidget : Gtk.Widget {
+       public abstract bool block_autohide { get; }
+}