Add the ability to load multiple apps into app_shell.

extensions/shell/browser/shell_desktop_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 EXTENSIONS_SHELL_BROWSER_SHELL_DESKTOP_CONTROLLER_H_
 #define EXTENSIONS_SHELL_BROWSER_SHELL_DESKTOP_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 51 matching lines @@
                                public aura::WindowTreeHostObserver {
  public:
   ShellDesktopController();
   virtual ~ShellDesktopController();
 
   // DesktopController:
   virtual aura::WindowTreeHost* GetHost() override;
   virtual AppWindow* CreateAppWindow(content::BrowserContext* context,
                                      const Extension* extension) override;
   virtual void AddAppWindow(aura::Window* window) override;
+  virtual void RemoveAppWindow(AppWindow* window) override;
   virtual void CloseAppWindows() override;
 
   // aura::client::WindowTreeClient overrides:
   virtual aura::Window* GetDefaultParent(aura::Window* context,
                                          aura::Window* window,
                                          const gfx::Rect& bounds) override;
 
 #if defined(OS_CHROMEOS)
   // chromeos::PowerManagerClient::Observer overrides:
   virtual void PowerButtonEventReceived(bool down,
@@ skipping 42 matching lines @@
 
   scoped_ptr<wm::CursorManager> cursor_manager_;
 
   scoped_ptr<wm::UserActivityDetector> user_activity_detector_;
 #if defined(OS_CHROMEOS)
   scoped_ptr<ui::UserActivityPowerManagerNotifier> user_activity_notifier_;
 #endif
 
   scoped_ptr<AppWindowClient> app_window_client_;
 
-  // The desktop supports a single app window.
-  AppWindow* app_window_;  // NativeAppWindow::Close() deletes this.
+  // NativeAppWindow::Close() deletes the AppWindow.
+  std::vector<AppWindow*> app_windows_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDesktopController);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_SHELL_BROWSER_SHELL_DESKTOP_CONTROLLER_H_