Separate athena's startup process from AppShell's

extensions/shell/browser/desktop_controller.h

Index: extensions/shell/browser/desktop_controller.h
diff --git a/extensions/shell/browser/desktop_controller.h b/extensions/shell/browser/desktop_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..950320c646c55ce38c8f8f50262610469f369f7b
--- /dev/null
+++ b/extensions/shell/browser/desktop_controller.h
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+// 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 EXTENSIONS_SHELL_BROWSER_DESKTOP_CONTROLLER_H_
+#define EXTENSIONS_SHELL_BROWSER_DESKTOP_CONTROLLER_H_
+
+namespace aura {
+class WindowTreeHost;
+}
+
+namespace content {
+class BrowserContext;
+}
+
+namespace extensions {
+class Extension;
+class ShellAppWindow;
+
+// DesktopController is an interface to construct the window environment in
+// extensions shell. ShellDesktopController provides a default implementation
+// for
+// app_shell, and embedder (such as athena) can provide its own.
+class DesktopController {
+ public:
+  DesktopController();
+  virtual ~DesktopController();
+
+  // Returns the single instance of the desktop. (Stateless functions like
+  // ShellAppWindowCreateFunction need to be able to access the desktop, so
+  // we need a singleton somewhere).
+  static DesktopController* instance();
+
+  // Returns the WindowTreeHost created by this DesktopController.
+  virtual aura::WindowTreeHost* GetHost() = 0;
+
+  // Creates a new app window and adds it to the desktop. The desktop maintains
+  // ownership of the window. The window must be closed before |extension| is
+  // destroyed.
+  virtual ShellAppWindow* CreateAppWindow(content::BrowserContext* context,
+                                          const Extension* extension) = 0;
+
+  // Closes and destroys the app windows.
+  virtual void CloseAppWindows() = 0;
+};
+
+}  // namespace extensinos
+
+#endif  // EXTENSIONS_SHELL_BROWSER_DESKTOP_CONTROLLER_H_