Second attempt at moving the StackingClient to a property on the RootWindow.

ui/aura_shell/stacking_controller.h

Index: ui/aura_shell/stacking_controller.h
===================================================================
--- ui/aura_shell/stacking_controller.h	(revision 114527)
+++ ui/aura_shell/stacking_controller.h	(working copy)
@@ -16,17 +16,14 @@
 
 class AlwaysOnTopController;
 
-class StackingController : public aura::StackingClient {
+class StackingController : public aura::client::StackingClient {
  public:
   StackingController();
   virtual ~StackingController();
 
-  // Initializes this controller.
-  void Init();
+  // Overridden from aura::client::StackingClient:
+  virtual aura::Window* GetDefaultParent(aura::Window* window) OVERRIDE;
 
-  // Overridden from aura::StackingClient:
-  virtual void AddChildToDefaultParent(aura::Window* window) OVERRIDE;
-
  private:
   // Returns corresponding modal container for a modal window.
   // If screen lock is not active, all modal windows are placed into the