app_list: Add search box and search result view for v2.

ui/app_list/search_box_view_delegate.h

+// Copyright (c) 2012 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_SEARCH_BOX_VIEW_DELEGATE_H_
+#define UI_APP_LIST_SEARCH_BOX_VIEW_DELEGATE_H_
+#pragma once
+
+#include "ui/app_list/app_list_export.h"
+
+namespace app_list {
+
+class SearchBoxView;
+
+class APP_LIST_EXPORT SearchBoxViewDelegate {
+ public:
+  // Invoked when query text has changed by the user.
+  virtual void QueryChanged(SearchBoxView* sender) = 0;
+
+ protected:
+  virtual ~SearchBoxViewDelegate() {}
+};
+
+}  // namespace ash
+
+#endif  // UI_APP_LIST_SEARCH_BOX_VIEW_DELEGATE_H_