ash: Update app list button.

ash/wm/app_list_controller_observer.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_APP_LIST_CONTROLLER_OBSERVER_H_
+#define ASH_WM_APP_LIST_CONTROLLER_OBSERVER_H_
+
+namespace aura {
+class RootWindow;
+}
+
+namespace ash {
+namespace internal {
+
+class AppListControllerObserver {
+ public:
+  // Invoked when app launcher bubble is toggled on the given root window.
+  virtual void OnAppLauncherVisibilityChanged(
+      bool visible,
+      const aura::RootWindow* root_window) = 0;
+
+ protected:
+  virtual ~AppListControllerObserver() {}
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_APP_LIST_CONTROLLER_OBSERVER_H_