Add workspace to desktop

ui/aura_shell/shell.h

Index: ui/aura_shell/shell.h
diff --git a/ui/aura_shell/shell.h b/ui/aura_shell/shell.h
index 114ee02acbe6895778285716d78d2ebfa05bbe4b..c7a2700e0038ae38c65a5fbe19dda76bbea289cf 100644
--- a/ui/aura_shell/shell.h
+++ b/ui/aura_shell/shell.h
@@ -28,6 +28,7 @@ namespace aura_shell {
 
 class Launcher;
 class ShellDelegate;
+class WorkspaceManager;
 
 // Shell is a singleton object that presents the Shell API and implements the
 // Desktop's delegate interface.
@@ -49,8 +50,8 @@ class AURA_SHELL_EXPORT Shell : public aura::DesktopDelegate {
   aura::Window* GetContainer(int container_id);
   const aura::Window* GetContainer(int container_id) const;
 
-  void TileWindows();
-  void RestoreTiledWindows();
+  // Toggles between overview mode and normal mode.
+  void ToggleOverview();
 
   Launcher* launcher() { return launcher_.get(); }
 
@@ -72,6 +73,8 @@ class AURA_SHELL_EXPORT Shell : public aura::DesktopDelegate {
 
   scoped_ptr<Launcher> launcher_;
 
+  scoped_ptr<WorkspaceManager> workspace_manager_;
+
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };