window-list: Always use ShellApp icon rather than _NET_WM_ICON

We currently use the application icon for items that are grouped
by application and the window icon otherwise. However with the
icon property being unused anywhere else in GNOME3, applications
have started to not set any window icon at all.
Rather than complaining to application authors, switch to using
the app icon everywhere, which improves consistency with the rest
of GNOME3 anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=694850

extensions/window-list/extension.js

@@ -14,6 +14,8 @@ const ExtensionUtils = imports.misc.extensionUtils;
 const Me = ExtensionUtils.getCurrentExtension();
 const Convenience = Me.imports.convenience;
 
+const ICON_TEXTURE_SIZE = 24;
+
 const GroupingMode = {
     NEVER: 0,
     ALWAYS: 1
@@ -37,10 +39,9 @@ const WindowTitle = new Lang.Class({
         this._metaWindow = metaWindow;
         this.actor = new St.BoxLayout();
 
-        let textureCache = St.TextureCache.get_default();
-        let icon = textureCache.bind_pixbuf_property(this._metaWindow, "icon");
+        let app = Shell.WindowTracker.get_default().get_window_app(metaWindow);
         this._icon = new St.Bin({ style_class: 'window-button-icon',
-                                  child: icon });
+                                  child: app.create_icon_texture(ICON_TEXTURE_SIZE) });
         this.actor.add(this._icon);
         this._label = new St.Label();
         this.actor.add(this._label);
@@ -165,7 +166,7 @@ const AppButton = new Lang.Class({
         stack.add_actor(this._multiWindowTitle);
 
         let icon = new St.Bin({ style_class: 'window-button-icon',
-                                child: app.create_icon_texture(24) });
+                                child: app.create_icon_texture(ICON_TEXTURE_SIZE) });
         this._multiWindowTitle.add(icon);
         this._multiWindowTitle.add(new St.Label({ text: app.get_name() }));