background: refresh background on gl-video-memory-purged signal

Right now we refresh the background when resuming and when NVIDIA.
But mutter has a signal to tell us specifically when to refresh,
and the signal is only emitted for NVIDIA, so use that instead.

js/ui/background.js

@@ -539,10 +539,15 @@ var BackgroundSource = new Lang.Class({
         this._backgrounds = [];
 
         this._monitorsChangedId = global.screen.connect('monitors-changed',
-                                                        this._onMonitorsChanged.bind(this));
+                                                        this._refresh.bind(this));
+
+        global.display.connect('gl-video-memory-purged', () => {
+                                   Meta.Background.refresh_all();
+                                   this._refresh();
+                               });
     },
 
-    _onMonitorsChanged() {
+    _refresh() {
         for (let monitorIndex in this._backgrounds) {
             let background = this._backgrounds[monitorIndex];
 

js/ui/layout.js

@@ -278,18 +278,6 @@ var LayoutManager = new Lang.Class({
         global.screen.connect('in-fullscreen-changed',
                               this._updateFullscreen.bind(this));
         this._monitorsChanged();
-
-        // NVIDIA drivers don't preserve FBO contents across
-        // suspend/resume, see
-        // https://bugzilla.gnome.org/show_bug.cgi?id=739178
-        if (Shell.util_need_background_refresh()) {
-            LoginManager.getLoginManager().connect('prepare-for-sleep',
-                (lm, suspending) => {
-                    if (suspending)
-                        return;
-                    Meta.Background.refresh_all();
-                });
-        }
     },
 
     // This is called by Main after everything else is constructed

src/shell-util.c

@@ -396,15 +396,6 @@ get_gl_vendor (void)
   return vendor;
 }
 
-gboolean
-shell_util_need_background_refresh (void)
-{
-  if (g_strcmp0 (get_gl_vendor (), "NVIDIA Corporation") == 0)
-    return TRUE;
-
-  return FALSE;
-}
-
 static gboolean
 canvas_draw_cb (ClutterContent *content,
                 cairo_t        *cr,