Adds code for a new Aura shell.

ui/aura/window.h

Index: ui/aura/window.h
===================================================================
--- ui/aura/window.h	(revision 101422)
+++ ui/aura/window.h	(working copy)
@@ -25,6 +25,7 @@
 
 class Desktop;
 class KeyEvent;
+class LayoutManager;
 class MouseEvent;
 class WindowDelegate;
 class WindowManager;
@@ -65,6 +66,8 @@
   void SetVisibility(Visibility visibility);
   Visibility visibility() const { return visibility_; }
 
+  void SetLayoutManager(LayoutManager* layout_manager);
+
   // Changes the bounds of the window.
   void SetBounds(const gfx::Rect& bounds, int anim_ms);
   const gfx::Rect& bounds() const { return bounds_; }
@@ -155,6 +158,7 @@
   int id_;
 
   scoped_ptr<WindowManager> window_manager_;
+  scoped_ptr<LayoutManager> layout_manager_;
 
   void* user_data_;