Implement app list folder management page UI.

ui/app_list/views/app_list_main_view.cc

 // 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.
 
 #include "ui/app_list/views/app_list_main_view.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
 #include "ui/app_list/app_list_constants.h"
+#include "ui/app_list/app_list_folder_item.h"
 #include "ui/app_list/app_list_item_model.h"
 #include "ui/app_list/app_list_model.h"
 #include "ui/app_list/app_list_view_delegate.h"
 #include "ui/app_list/pagination_model.h"
 #include "ui/app_list/search_box_model.h"
 #include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/contents_view.h"
 #include "ui/app_list/views/search_box_view.h"
 #include "ui/views/controls/textfield/textfield.h"
 #include "ui/views/layout/box_layout.h"
@@ skipping 158 matching lines @@
   DCHECK(it != pending_icon_loaders_.end());
   pending_icon_loaders_.erase(it);
 
   if (pending_icon_loaders_.empty() && icon_loading_wait_timer_.IsRunning()) {
     icon_loading_wait_timer_.Stop();
     GetWidget()->Show();
   }
 }
 
 void AppListMainView::ActivateApp(AppListItemModel* item, int event_flags) {
-  item->Activate(event_flags);
+  // TODO(jennyz): Activate the folder via AppListModel notification.
+  if (item->GetAppType() == AppListFolderItem::kAppType)
+    contents_view_->ShowFolderContent(static_cast<AppListFolderItem*>(item));
+  else
+    item->Activate(event_flags);
 }
 
 void AppListMainView::GetShortcutPathForApp(
     const std::string& app_id,
     const base::Callback<void(const base::FilePath&)>& callback) {
   if (delegate_) {
     delegate_->GetShortcutPathForApp(app_id, callback);
     return;
   }
   callback.Run(base::FilePath());
@@ skipping 35 matching lines @@
   // Resubmit the query via a posted task so that all observers for the
   // uninstall notification are notified.
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&AppListMainView::QueryChanged,
                  weak_ptr_factory_.GetWeakPtr(),
                  search_box_view_));
 }
 
 }  // namespace app_list