[gnome-mahjongg] snap: Update yaml to use GNOME extension

[Ken VanDine <kvandine src gnome org>]

commit 33b8f36f8decd138e2143d5661436abbee28b944
Author: Heather Ellsworth <hellsworth gnome org>
Date:   Tue Sep 24 20:22:13 2019 +0000

    snap: Update yaml to use GNOME extension

 snap/snapcraft.yaml | 33 ++-------------------------------
 1 file changed, 2 insertions(+), 31 deletions(-)
---
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index 09ae41f..7c71295 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -17,20 +17,6 @@ grade: stable # must be 'stable' to release into candidate/stable channels
 confinement: strict
 base: core18
 
-plugs:
-  gnome-3-28-1804:
-    interface: content
-    target: $SNAP/gnome-platform
-    default-provider: gnome-3-28-1804
-  gtk-3-themes:
-    interface: content
-    target: $SNAP/data-dir/themes
-    default-provider: gtk-common-themes
-  icon-themes:
-    interface: content
-    target: $SNAP/data-dir/icons
-    default-provider: gtk-common-themes
-
 slots:
   # for GtkApplication registration
   gnome-mahjongg:
@@ -40,29 +26,14 @@ slots:
 
 apps:
   gnome-mahjongg:
-    command: desktop-launch gnome-mahjongg
+    command: usr/bin/gnome-mahjongg
+    extensions: [gnome-3-28]
     plugs:
-      - desktop
-      - desktop-legacy
       - gsettings
-      - unity7
-      - wayland
     desktop: usr/share/applications/org.gnome.Mahjongg.desktop
 
 parts:
-  desktop-gnome-platform:
-    source: https://github.com/ubuntu/snapcraft-desktop-helpers.git
-    source-subdir: gtk
-    plugin: make
-    make-parameters: ["FLAVOR=gtk3"]
-    build-packages:
-      - build-essential
-      - libgtk-3-dev
-    override-build: |
-      snapcraftctl build
-      mkdir -pv $SNAPCRAFT_PART_INSTALL/gnome-platform
   gnome-mahjongg:
-    after: [desktop-gnome-platform]
     source: .
     source-type: git
     override-build: |