Introduces AppActivity and handler of chrome.shell API.

apps/shell/browser/shell_app_window_controller.h

+// Copyright 2014 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 APPS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_
+#define APPS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_
+
+namespace content {
+class BrowserContext;
+}
+
+namespace apps {
+
+class ShellAppWindow;
+
+class ShellAppWindowController {
+ public:
+  virtual ~ShellAppWindowController() {}
+
+  // Creates a new app window and adds it to the desktop. This class should
+  // maintain the ownership of the window.
+  virtual ShellAppWindow* CreateAppWindow(content::BrowserContext* context) = 0;
+
+  // Closes and destroys the app windows.
+  virtual void CloseAppWindows() = 0;
+};
+
+}  // namespace apps
+
+#endif  // APPS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_