Implement app list folder management page UI.

ui/app_list/views/folder_header_view_delegate.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 UI_APP_LIST_VIEWS_FOLDER_HEADER_VIEW_DELEGATE_H_
+#define UI_APP_LIST_VIEWS_FOLDER_HEADER_VIEW_DELEGATE_H_
+
+namespace app_list {
+
+class AppListFolderItem;
+
+class FolderHeaderViewDelegate {
+ public:
+  // Invoked when the back button on the folder header view is clicked.
+  // |item| is the folder item which FolderHeaderview represents.
+  // |event_flags| contains the flags of the keyboard/mouse event that triggers
+  // the request.
+  virtual void NavigateBack(AppListFolderItem* item,
+                            const ui::Event& event_flags) = 0;
+
+ protected:
+  virtual ~FolderHeaderViewDelegate() {}
+};
+
+}  // namespace app_list
+
+#endif  // UI_APP_LIST_VIEWS_FOLDER_HEADER_VIEW_DELEGATE_H_