Adds AppListDelegate to AppList that is notified on visibility changes

ash/app_list/app_list_delegate_impl.h

Index: ash/app_list/app_list_delegate_impl.h
diff --git a/ash/app_list/app_list_delegate_impl.h b/ash/app_list/app_list_delegate_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..d7b1fee0d92bdc1a33a7826fdb10727b4de26be7
--- /dev/null
+++ b/ash/app_list/app_list_delegate_impl.h
@@ -0,0 +1,28 @@
+// Copyright 2017 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_APP_LIST_APP_LIST_DELEGATE_IMPL_H_
+#define ASH_APP_LIST_APP_LIST_DELEGATE_IMPL_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "ui/app_list/presenter/app_list_delegate.h"
+
+namespace ash {
+
+class ASH_EXPORT AppListDelegateImpl : public app_list::AppListDelegate {
+ public:
+  explicit AppListDelegateImpl();
+  ~AppListDelegateImpl() override;
+
+ private:
+  // app_list::AppListDelegate:
+  void OnAppListVisibilityChanged(bool visible, int64_t display_id) override;
+
+  DISALLOW_COPY_AND_ASSIGN(AppListDelegateImpl);
+};
+
+}  // namespace ash
+
+#endif  // ASH_APP_LIST_APP_LIST_DELEGATE_IMPL_H_