Close app list widget when users click outside of the widget

ui/app_list/presenter/app_list_presenter_impl.h

 // Copyright 2016 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 UI_APP_LIST_PRESENTER_APP_LIST_PRESENTER_IMPL_H_
 #define UI_APP_LIST_PRESENTER_APP_LIST_PRESENTER_IMPL_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
@@ skipping 35 matching lines @@
   ~AppListPresenterImpl() override;
 
   // Returns app list window or NULL if it is not visible.
   aura::Window* GetWindow();
 
   // Returns app list view if one exists, or NULL otherwise.
   AppListView* GetView() { return view_; }
 
   // AppListPresenter:
   void Show(int64_t display_id) override;
-  void Dismiss() override;
+  void Dismiss() final;
   void ToggleAppList(int64_t display_id) override;
   bool IsVisible() const override;
   bool GetTargetVisibility() const override;
 
  private:
   friend class test::AppListPresenterImplTestApi;
 
   // Sets the app list view and attempts to show it.
   void SetView(AppListView* view);
 
@@ skipping 45 matching lines @@
 
   // Whether should schedule snap back animation.
   bool should_snap_back_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(AppListPresenterImpl);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_PRESENTER_APP_LIST_PRESENTER_IMPL_H_