background: Remove sheen overlay

The metaphor was valid when we used a monitor to display the preview
but now it doesn't work. There is no glass to reflect light. It
distracts from the preview and may look like a defect.

https://bugzilla.gnome.org/show_bug.cgi?id=676539

panels/background/Makefile.am

@@ -3,8 +3,7 @@ cappletname = background
 
 uidir = $(pkgdatadir)/ui/background
 dist_ui_DATA = \
-	background.ui \
-	display-overlay.png
+	background.ui
 
 slideshowicondir = $(datadir)/icons/hicolor/scalable/categories/
 dist_slideshowicon_DATA = slideshow-symbolic.svg

panels/background/cc-background-panel.c

@@ -62,7 +62,6 @@ struct _CcBackgroundPanelPrivate
 
   GtkWidget *spinner;
 
-  GdkPixbuf *display_overlay;
   GdkPixbuf *display_screenshot;
   char *screenshot_path;
 };
@@ -110,12 +109,6 @@ cc_background_panel_dispose (GObject *object)
       priv->thumb_factory = NULL;
     }
 
-  if (priv->display_overlay)
-    {
-      g_object_unref (priv->display_overlay);
-      priv->display_overlay = NULL;
-    }
-
   if (priv->display_screenshot)
     {
       g_object_unref (priv->display_screenshot);
@@ -246,14 +239,6 @@ update_display_preview (CcBackgroundPanel *panel)
       cairo_paint (cr);
     }
 
-  if (priv->display_overlay)
-    {
-      gdk_cairo_set_source_pixbuf (cr,
-                                   priv->display_overlay,
-                                   0, 0);
-      cairo_paint (cr);
-    }
-
   cairo_destroy (cr);
 }
 
@@ -728,10 +713,6 @@ cc_background_panel_init (CcBackgroundPanel *self)
 
   priv->copy_cancellable = g_cancellable_new ();
 
-  priv->display_overlay = gdk_pixbuf_new_from_file (DATADIR
-                                                    "/display-overlay.png",
-                                                    NULL);
-
   priv->thumb_factory = gnome_desktop_thumbnail_factory_new (GNOME_DESKTOP_THUMBNAIL_SIZE_LARGE);
 
   load_current_bg (self);