[gnome-music/wip/jfelder/headerbar-smooth-transition: 7/7] headerbar: Smooth selection-mode transition

[Jean Felder <jfelder src gnome org>]

commit e76c86ed9b1205127370d8bbc61f813e6cc68339
Author: Jean Felder <jfelder src gnome org>
Date:   Tue Jun 19 17:43:07 2018 +0200

    headerbar: Smooth selection-mode transition
    
    Add a smooth transition to and from blue in the HeaderBar, while switching
    selection mode.
    Transition duration is equal to the SelectionToolbar reveal.
    
    Closes: #27

 data/application.css | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/data/application.css b/data/application.css
index 89fc2056..26d30d7f 100644
--- a/data/application.css
+++ b/data/application.css
@@ -130,3 +130,8 @@ box#ArtistAlbumsWidget .artist-label {
                                                 alpha(@theme_selected_bg_color, 0.27) 2px,
                                                 alpha(@theme_selected_bg_color, 0.20) 3px);
 }
+
+/* headerbar - smooth selection-mode transition */
+headerbar {
+    transition: 250ms ease-in-out;
+}