Rename StackingClient -> WindowTreeClient

ash/wm/stacking_controller.h

Index: ash/wm/stacking_controller.h
diff --git a/ash/wm/stacking_controller.h b/ash/wm/stacking_controller.h
index 07003cbecedd7d591a741487fc8fe01eb6049013..0aa690eee4046d5bf5112e343b888669cf61a366 100644
--- a/ash/wm/stacking_controller.h
+++ b/ash/wm/stacking_controller.h
@@ -9,7 +9,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
-#include "ui/aura/client/stacking_client.h"
+#include "ui/aura/client/window_tree_client.h"
 
 namespace aura{
 class RootWindow;
@@ -21,12 +21,12 @@ namespace internal {
 class AlwaysOnTopController;
 }
 
-class ASH_EXPORT StackingController : public aura::client::StackingClient {
+class ASH_EXPORT StackingController : public aura::client::WindowTreeClient {
  public:
   StackingController();
   virtual ~StackingController();
 
-  // Overridden from aura::client::StackingClient:
+  // Overridden from aura::client::WindowTreeClient:
   virtual aura::Window* GetDefaultParent(aura::Window* context,
                                          aura::Window* window,
                                          const gfx::Rect& bounds) OVERRIDE;